词汇表 ¶

>>> ¶

The default Python prompt of the interactive shell. Often seen for code examples which can be executed interactively in the interpreter.

... ¶

Can refer to:

• The default Python prompt of the interactive shell when entering the code for an indented code block, when within a pair of matching left and right delimiters (parentheses, square brackets, curly braces or triple quotes), or after specifying a decorator.

• Ellipsis 内置常量。

2to3 ¶

A tool that tries to convert Python 2.x code to Python 3.x code by handling most of the incompatibilities which can be detected by parsing the source and traversing the parse tree.

2to3 可用于标准库作为 lib2to3 ；独立入口点的提供作为 Tools/scripts/2to3 。见 2to3 — 自动 Python 2 到 3 代码翻译 .

抽象基类 ¶

抽象基类补充 鸭子类型 通过提供接口定义方式，当其它技术像 hasattr() would be clumsy or subtly wrong (for example with magic methods ). ABCs introduce virtual subclasses, which are classes that don’t inherit from a class but are still recognized by isinstance() and issubclass() ；见 abc module documentation. Python comes with many built-in ABCs for data structures (in the collections.abc module), numbers (in the numbers module), streams (in the io module), import finders and loaders (in the importlib.abc module). You can create your own ABCs with the abc 模块。

annotation ¶

A label associated with a variable, a class attribute or a function parameter or return value, used by convention as a 类型提示 .

Annotations of local variables cannot be accessed at runtime, but annotations of global variables, class attributes, and functions are stored in the __annotations__ special attribute of modules, classes, and functions, respectively.

见 变量注解 , 函数注解 , PEP 484 and PEP 526 , which describe this functionality. Also see 注解最佳实践 for best practices on working with annotations.

argument ¶

值被传递给 function (或 方法 ) 当调用函数时。有 2 种自变量：

• 关键词自变量 : an argument preceded by an identifier (e.g. name= ) in a function call or passed as a value in a dictionary preceded by ** 。例如， 3 and 5 are both keyword arguments in the following calls to complex() :

  complex(real=3, imag=5)
  complex(**{'real': 3, 'imag': 5})
  								

• 位置自变量 : an argument that is not a keyword argument. Positional arguments can appear at the beginning of an argument list and/or be passed as elements of an iterable preceded by * 。例如， 3 and 5 are both positional arguments in the following calls:

  complex(3, 5)
  complex(*(3, 5))
  								

Arguments are assigned to the named local variables in a function body. See the 调用 section for the rules governing this assignment. Syntactically, any expression can be used to represent an argument; the evaluated value is assigned to the local variable.

另请参阅 参数 词汇表条目，FAQ 问题有关 自变量和参数之间的差异 ，和 PEP 362 .

异步上下文管理器 ¶

An object which controls the environment seen in an async with 语句通过定义 __aenter__() and __aexit__() 方法。引入通过 PEP 492 .

异步生成器 ¶

A function which returns an 异步生成器迭代器 . It looks like a coroutine function defined with async def except that it contains yield expressions for producing a series of values usable in an async for 循环。

Usually refers to an asynchronous generator function, but may refer to an 异步生成器迭代器 在某些上下文中。若欲表达含义不清晰，使用完整术语避免歧义。

An asynchronous generator function may contain await 表达式及 async for ，和 async with 语句。

异步生成器迭代器 ¶

对象的创建通过 异步生成器 函数。

这是 异步迭代器 which when called using the __anext__() method returns an awaitable object which will execute the body of the asynchronous generator function until the next yield 表达式。

每个 yield 会临时挂起处理，记住定位执行状态 (包括局部变量和待决 try 语句)。当 异步生成器迭代器 effectively resumes with another awaitable returned by __anext__() , it picks up where it left off. See PEP 492 and PEP 525 .

异步可迭代 ¶

对象，可用于 async for 语句。必须返回 异步迭代器 从其 __aiter__() 方法。引入通过 PEP 492 .

异步迭代器 ¶

对象有实现 __aiter__() and __anext__() 方法。 __anext__ 必须返回 awaitable 对象。 async for resolves the awaitables returned by an asynchronous iterator’s __anext__() 方法直到它引发 StopAsyncIteration 异常。引入通过 PEP 492 .

属性 ¶

A value associated with an object which is usually referenced by name using dotted expressions. For example, if an object o has an attribute a it would be referenced as o.a .

It is possible to give an object an attribute whose name is not an identifier as defined by 标识符和关键词 , for example using setattr() , if the object allows it. Such an attribute will not be accessible using a dotted expression, and would instead need to be retrieved with getattr() .

awaitable ¶

对象可用于 await 表达式。可以是 协程 或对象具有 __await__() 方法。另请参阅 PEP 492 .

BDFL ¶

仁慈的终生独裁者，也称为 Guido van Rossum ，Python 的创建者。

二进制文件 ¶

文件对象 能读取和写入 像字节对象 。二进制文件的范例是以二进制模式打开的文件 ( 'rb' , 'wb' or 'rb+' ), sys.stdin.buffer , sys.stdout.buffer ，和实例化的 io.BytesIO and gzip.GzipFile .

另请参阅 文本文件 为文件对象能读取和写入 str 对象。

借位引用 ¶

In Python’s C API, a borrowed reference is a reference to an object. It does not modify the object reference count. It becomes a dangling pointer if the object is destroyed. For example, a garbage collection can remove the last 强引用 to the object and so destroy it.

调用 Py_INCREF() 在 借位引用 is recommended to convert it to a 强引用 in-place, except when the object cannot be destroyed before the last usage of the borrowed reference. The Py_NewRef() function can be used to create a new 强引用 .

像字节对象 ¶

对象支持 缓冲协议 且可以导出 C contiguous 缓冲。这包括所有 bytes , bytearray ，和 array.array objects, as well as many common memoryview objects. Bytes-like objects can be used for various operations that work with binary data; these include compression, saving to a binary file, and sending over a socket.

Some operations need the binary data to be mutable. The documentation often refers to these as “read-write bytes-like objects”. Example mutable buffer objects include bytearray 和 memoryview 的 bytearray . Other operations require the binary data to be stored in immutable objects (“read-only bytes-like objects”); examples of these include bytes 和 memoryview 的 bytes 对象。

bytecode ¶

Python source code is compiled into bytecode, the internal representation of a Python program in the CPython interpreter. The bytecode is also cached in .pyc files so that executing the same file is faster the second time (recompilation from source to bytecode can be avoided). This “intermediate language” is said to run on a 虚拟机 that executes the machine code corresponding to each bytecode. Do note that bytecodes are not expected to work between different Python virtual machines, nor to be stable between Python releases.

A list of bytecode instructions can be found in the documentation for dis 模块 .

callable ¶

可调用是可以被调用的对象，可能具有一组自变量 (见 argument )，采用以下句法：

callable(argument1, argument2, ...)
						

function ，和扩展 方法 是可调用。类实例有实现 __call__() 方法也是可调用。

callback ¶

作为自变量被传递，以在未来某个时刻被执行的子例程函数。

class ¶

用于创建用户定义对象的模板。类定义通常包含运转于类实例的方法定义。

类变量 ¶

在类中定义，且仅旨在类级别 (即：不在类实例中) 修改的变量。

复数 ¶

An extension of the familiar real number system in which all numbers are expressed as a sum of a real part and an imaginary part. Imaginary numbers are real multiples of the imaginary unit (the square root of -1 ), often written i in mathematics or j in engineering. Python has built-in support for complex numbers, which are written with this latter notation; the imaginary part is written with a j suffix, e.g., 3+1j . To get access to complex equivalents of the math 模块，使用 cmath . Use of complex numbers is a fairly advanced mathematical feature. If you’re not aware of a need for them, it’s almost certain you can safely ignore them.

上下文管理器 ¶

控制所见环境的对象在 with 语句通过定义 __enter__() and __exit__() 方法。见 PEP 343 .

上下文变量 ¶

A variable which can have different values depending on its context. This is similar to Thread-Local Storage in which each execution thread may have a different value for a variable. However, with context variables, there may be several contexts in one execution thread and the main usage for context variables is to keep track of variables in concurrent asynchronous tasks. See contextvars .

contiguous ¶

准确认为缓冲是连续的，若它是 C-contiguous or Fortran contiguous . Zero-dimensional buffers are C and Fortran contiguous. In one-dimensional arrays, the items must be laid out in memory next to each other, in order of increasing indexes starting from zero. In multidimensional C-contiguous arrays, the last index varies the fastest when visiting items in order of memory address. However, in Fortran contiguous arrays, the first index varies the fastest.

协程 ¶

协程是更一般化形式的子例程。子例程在一个点进入，和在另一点退出。协程可以在许多不同点进入、退出和再继续。可以实现它们采用 async def 语句。另请参阅 PEP 492 .

协程函数 ¶

函数返回 协程 对象。协程函数的定义可以采用 async def 语句，且可能包含 await , async for ，和 async with 关键词。这些的引入是通过 PEP 492 .

CPython ¶

Python 编程语言的典型实现，作为分发在 python.org 。当有必要时使用 CPython 术语以区分这种实现与其它实现，譬如：Jython 或 IronPython。

装饰器 ¶

返回另一函数的函数，通常作为函数变换运用，使用 @wrapper 句法。装饰器的常见范例是 classmethod() and staticmethod() .

装饰器句法仅仅是句法糖，以下 2 函数定义在语义上是等效的：

def f(arg):
    ...
f = staticmethod(f)
@staticmethod
def f(arg):
    ...
						

类存在同样的概念，但很少使用。见文档编制为 函数定义 and 类定义 了解有关装饰器的更多信息。

descriptor ¶

任何对象若有定义方法 __get__() , __set__() ，或 __delete__() . When a class attribute is a descriptor, its special binding behavior is triggered upon attribute lookup. Normally, using a.b to get, set or delete an attribute looks up the object named b in the class dictionary for a , but if b is a descriptor, the respective descriptor method gets called. Understanding descriptors is a key to a deep understanding of Python because they are the basis for many features including functions, methods, properties, class methods, static methods, and reference to super classes.

有关描述符方法的更多信息，见 实现描述符 或 描述符怎么样指南 .

dictionary ¶

An associative array, where arbitrary keys are mapped to values. The keys can be any object with __hash__() and __eq__() methods. Called a hash in Perl.

字典推导 ¶

A compact way to process all or part of the elements in an iterable and return a dictionary with the results. results = {n: n ** 2 for n in range(10)} 生成字典包含键 n 映射到值 n ** 2 。见 显示列表、集和字典 .

字典视图 ¶

对象返回自 dict.keys() , dict.values() ，和 dict.items() are called dictionary views. They provide a dynamic view on the dictionary’s entries, which means that when the dictionary changes, the view reflects these changes. To force the dictionary view to become a full list use list(dictview) 。见 字典视图对象 .

docstring ¶

A string literal which appears as the first expression in a class, function or module. While ignored when the suite is executed, it is recognized by the compiler and put into the __doc__ attribute of the enclosing class, function or module. Since it is available via introspection, it is the canonical place for documentation of the object.

鸭子类型 ¶

A programming style which does not look at an object’s type to determine if it has the right interface; instead, the method or attribute is simply called or used (“If it looks like a duck and quacks like a duck, it must be a duck.”) By emphasizing interfaces rather than specific types, well-designed code improves its flexibility by allowing polymorphic substitution. Duck-typing avoids tests using type() or isinstance() . (Note, however, that duck-typing can be complemented with 抽象基类 .) Instead, it typically employs hasattr() tests or EAFP programming.

EAFP ¶

Easier to ask for forgiveness than permission. This common Python coding style assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false. This clean and fast style is characterized by the presence of many try and except statements. The technique contrasts with the LBYL style common to many other languages such as C.

表达式 ¶

A piece of syntax which can be evaluated to some value. In other words, an expression is an accumulation of expression elements like literals, names, attribute access, operators or function calls which all return a value. In contrast to many other languages, not all language constructs are expressions. There are also statement s which cannot be used as expressions, such as while . Assignments are also statements, not expressions.

扩展模块 ¶

以 C/C++ 编写的模块，使用 Python 的 C API 与核心和用户代码交互。

f-string ¶

字符串文字前缀采用 'f' or 'F' 通常称为 f-strings 是简写的 格式化字符串文字 。另请参阅 PEP 498 .

文件对象 ¶

对象暴露面向文件 API (采用方法，譬如 read() or write() ) 到底层资源。根据创建方式，文件对象可以中介访问真实磁盘文件、其它类型存储或通信设备 (例如：标准输入/输出、内存缓冲、套接字、管道、等)。文件对象也称 像文件对象 or 流 .

实际有 3 类文件对象：原生 二进制文件 ，缓冲 二进制文件 and 文本文件 。它们接口的定义在 io 模块。创建文件对象的典型方式是使用 open() 函数。

像文件对象 ¶

同义词 文件对象 .

文件系统编码和错误处理程序 ¶

编码和错误处理程序用于 Python 解码字节从操作系统和编码 Unicode 到操作系统。

文件系统编码必须保证成功解码 128 以下的所有字节。若文件系统编码提供此保证失败，API 函数会引发 UnicodeError .

sys.getfilesystemencoding() and sys.getfilesystemencodeerrors() 函数可以用于获取文件系统编码和错误处理程序。

文件系统编码和错误处理程序 的配置是在 Python 启动时通过 PyConfig_Read() 函数：见 filesystem_encoding and filesystem_errors 成员对于 PyConfig .

另请参阅 区域设置编码 .

finder ¶

对象试着查找 loader 为正导入模块。

从 Python 3.3 起，有 2 种类型的查找器： 元路径查找器 用于 sys.meta_path ，和 路径条目查找器 用于 sys.path_hooks .

见 PEP 302 , PEP 420 and PEP 451 了解更多细节。

floor division ¶

Mathematical division that rounds down to nearest integer. The floor division operator is // 。例如，表达式 11 // 4 评估为 2 in contrast to the 2.75 returned by float true division. Note that (-11) // 4 is -3 because that is -2.75 rounded downward 。见 PEP 238 .

function ¶

向调用者返回某值的一系列语句。也可以传递零个或多个 arguments 可以用于本体的执行。另请参阅 参数 , 方法 ，和 函数定义 章节。

函数注解 ¶

annotation 为函数参数或返回值。

函数注解通常用于 类型提示 ：例如，此函数期望接受两 int 自变量且还期望拥有 int 返回值：

def sum_two_numbers(a: int, b: int) -> int:
   return a + b
						

函数注解语法的解释在章节 函数定义 .

见 变量注解 and PEP 484 , which describe this functionality. Also see 注解最佳实践 for best practices on working with annotations.

__future__ ¶

A 未来语句 , from __future__ import <feature> , directs the compiler to compile the current module using syntax or semantics that will become standard in a future release of Python. The __future__ module documents the possible values of feature . By importing this module and evaluating its variables, you can see when a new feature was first added to the language and when it will (or did) become the default:

>>> import __future__
>>> __future__.division
_Feature((2, 2, 0, 'alpha', 2), (3, 0, 0, 'alpha', 0), 8192)
						

垃圾收集 ¶

释放内存的过程当不再使用时。Python 凭借引用计数及能够检测和中断引用循环的循环垃圾收集器来履行垃圾收集。垃圾收集器的控制是使用 gc 模块。

generator ¶

函数返回 生成器迭代器 。它看起来像正常函数，除了它包含 yield 表达式，用于产生可用于 for 循环的一系列值，或每次可以检索一值采用 next() 函数。

通常指生成器函数，但也可能指 生成器迭代器 在某些上下文中。若欲表达含义不清晰，使用完整术语避免歧义。

生成器迭代器 ¶

对象的创建通过 generator 函数。

每个 yield 会临时挂起处理，记住定位执行状态 (包括局部变量和待决 try 语句)。当 生成器迭代器 再继续时，它从它离开的地方 (相比每次援引都重新开始的函数) 捡起。

生成器表达式 ¶

An expression that returns an iterator. It looks like a normal expression followed by a for clause defining a loop variable, range, and an optional if clause. The combined expression generates values for an enclosing function:

>>> sum(i*i for i in range(10))         # sum of squares 0, 1, 4, ... 81
285
						

一般函数 ¶

A function composed of multiple functions implementing the same operation for different types. Which implementation should be used during a call is determined by the dispatch algorithm.

另请参阅 单次分派 词汇表条目， functools.singledispatch() 装饰器，和 PEP 443 .

一般类型 ¶

A type that can be parameterized; typically a 容器类 譬如 list or dict 。用于 类型提示 and annotations .

更多细节，见 generic alias types , PEP 483 , PEP 484 , PEP 585 ，和 typing 模块。

GIL ¶

见 全局解释器锁 .

全局解释器锁 ¶

机制用于 CPython 解释器担保只有一个线程执行 Python bytecode 每次。这简化 CPython 实现通过使对象模型 (包括关键内置类型，譬如 dict ) 隐含安全阻止并发访问。锁定整个解释器使解释器更易于多线程，以付出由多处理器机器提供的许多并行性为代价。

However, some extension modules, either standard or third-party, are designed so as to release the GIL when doing computationally intensive tasks such as compression or hashing. Also, the GIL is always released when doing I/O.

过去创建 "自由线程" 解释器 (以更细粒度锁定共享数据) 的努力并不成功，因为在常见单处理器情况下会损失性能。据信，克服此性能问题将使得实现更加复杂，因此维护更昂贵。

基于哈希的 pyc ¶

A bytecode cache file that uses the hash rather than the last-modified time of the corresponding source file to determine its validity. See 缓存字节码无效 .

hashable ¶

对象 hashable 若它拥有的哈希值在其寿命内从不改变 (它需要 __hash__() 方法)，且可以比较其它对象 (它需要 __eq__() 方法)。比较相等的可哈希对象必须拥有相同的哈希值。

可哈希性使对象可用作字典键和 set 成员，因为这些数据结构内部使用哈希值。

Most of Python’s immutable built-in objects are hashable; mutable containers (such as lists or dictionaries) are not; immutable containers (such as tuples and frozensets) are only hashable if their elements are hashable. Objects which are instances of user-defined classes are hashable by default. They all compare unequal (except with themselves), and their hash value is derived from their id() .

IDLE ¶

用于 Python 的集成开发和学习环境。 IDLE 是 Python 标准分发附带的基本编辑器和解释器环境。

immutable ¶

具有固定值的对象。不可变对象包括数字、字符串及元组。这种对象不可以变更。必须创建新对象，若必须存储不同值。它们在需要常量哈希值 (例如：作为字典键) 的地方扮演重要角色。

导入路径 ¶

A list of locations (or 路径条目 ) that are searched by the 基于路径的查找器 for modules to import. During import, this list of locations usually comes from sys.path , but for subpackages it may also come from the parent package’s __path__ 属性。

importing ¶

The process by which Python code in one module is made available to Python code in another module.

importer ¶

An object that both finds and loads a module; both a finder and loader 对象。

interactive ¶

Python has an interactive interpreter which means you can enter statements and expressions at the interpreter prompt, immediately execute them and see their results. Just launch python with no arguments (possibly by selecting it from your computer’s main menu). It is a very powerful way to test out new ideas or inspect modules and packages (remember help(x) ).

interpreted ¶

Python is an interpreted language, as opposed to a compiled one, though the distinction can be blurry because of the presence of the bytecode compiler. This means that source files can be run directly without explicitly creating an executable which is then run. Interpreted languages typically have a shorter development/debug cycle than compiled ones, though their programs generally also run more slowly. See also interactive .

解释器关闭 ¶

When asked to shut down, the Python interpreter enters a special phase where it gradually releases all allocated resources, such as modules and various critical internal structures. It also makes several calls to the 垃圾收集器 . This can trigger the execution of code in user-defined destructors or weakref callbacks. Code executed during the shutdown phase can encounter various exceptions as the resources it relies on may not function anymore (common examples are library modules or the warnings machinery).

The main reason for interpreter shutdown is that the __main__ module or the script being run has finished executing.

iterable ¶

每次能够返回一成员的对象。可迭代范例包括所有序列类型 (譬如 list , str ，和 tuple ) 和一些非序列类型像 dict , 文件对象 ，和任何类对象的定义是采用 __iter__() 方法或采用 __getitem__() 方法实现 sequence 语义。

Iterables can be used in a for loop and in many other places where a sequence is needed ( zip() , map() , …). When an iterable object is passed as an argument to the built-in function iter() , it returns an iterator for the object. This iterator is good for one pass over the set of values. When using iterables, it is usually not necessary to call iter() or deal with iterator objects yourself. The for statement does that automatically for you, creating a temporary unnamed variable to hold the iterator for the duration of the loop. See also iterator , sequence ，和 generator .

iterator ¶

表示数据流的对象。重复调用迭代器的 __next__() 方法 (或把它传递给内置函数 next() ) 会依次返回流中的项。当没有更多数据可用时 StopIteration 异常被引发取而代之。此时，迭代器对象耗尽，且任何进一步调用其 __next__() 方法仅仅引发 StopIteration 再次。要求迭代器拥有 __iter__() 方法返回迭代器对象本身，所以，每个迭代器也可迭代，且可以用于接受其它可迭代的大多数地方。试图多次迭代遍历的代码是一个值得注意的例外。容器对象 (譬如 list ) 将产生刷新的新迭代器，每次把它传递给 iter() 函数或把它用于 for 循环。采用迭代器尝试这将仅仅返回用于先前迭代遍历的同一耗尽迭代器对象，使它看起来像空容器。

可以找到更多信息在 迭代器类型 .

CPython 实现细节： CPython 并不一致应用要求迭代器定义 __iter__() .

关键函数 ¶

关键函数 (或整理函数) 是返回用于排序 (或次序) 值的可调用。例如， locale.strxfrm() 是用于产生特定区域设置排序约定意识的排序键。

A number of tools in Python accept key functions to control how elements are ordered or grouped. They include min() , max() , sorted() , list.sort() , heapq.merge() , heapq.nsmallest() , heapq.nlargest() ，和 itertools.groupby() .

There are several ways to create a key function. For example. the str.lower() method can serve as a key function for case insensitive sorts. Alternatively, a key function can be built from a lambda expression such as lambda r: (r[0], r[2]) . Also, operator.attrgetter() , operator.itemgetter() ，和 operator.methodcaller() are three key function constructors. See the 排序怎么样 for examples of how to create and use key functions.

关键词自变量 ¶

见 argument .

lambda ¶

An anonymous inline function consisting of a single 表达式 which is evaluated when the function is called. The syntax to create a lambda function is lambda [parameters]: expression

LBYL ¶

Look before you leap. This coding style explicitly tests for pre-conditions before making calls or lookups. This style contrasts with the EAFP approach and is characterized by the presence of many if 语句。

In a multi-threaded environment, the LBYL approach can risk introducing a race condition between “the looking” and “the leaping”. For example, the code, if key in mapping: return mapping[key] can fail if another thread removes key from mapping after the test, but before the lookup. This issue can be solved with locks or by using the EAFP approach.

区域设置编码 ¶

On Unix, it is the encoding of the LC_CTYPE locale. It can be set with locale.setlocale(locale.LC_CTYPE, new_locale) .

On Windows, it is the ANSI code page (ex: "cp1252" ).

在 Android 和 VxWorks，Python 使用 "utf-8" 作为区域设置编码。

locale.getencoding() can be used to get the locale encoding.

另请参阅 文件系统编码和错误处理程序 .

list ¶

内置 Python sequence . Despite its name it is more akin to an array in other languages than to a linked list since access to elements is O(1).

列表推导 ¶

A compact way to process all or part of the elements in a sequence and return a list with the results. result = ['{:#04x}'.format(x) for x in range(256) if x % 2 == 0] generates a list of strings containing even hex numbers (0x..) in the range from 0 to 255. The if clause is optional. If omitted, all elements in range(256) are processed.

loader ¶

An object that loads a module. It must define a method named load_module() . A loader is typically returned by a finder 。见 PEP 302 for details and importlib.abc.Loader 对于 抽象基类 .

magic method ¶

An informal synonym for 特殊方法 .

映射 ¶

A container object that supports arbitrary key lookups and implements the methods specified in the collections.abc.Mapping or collections.abc.MutableMapping 抽象基类 。范例包括 dict , collections.defaultdict , collections.OrderedDict and collections.Counter .

元路径查找器 ¶

A finder returned by a search of sys.meta_path . Meta path finders are related to, but different from 路径条目查找器 .

见 importlib.abc.MetaPathFinder for the methods that meta path finders implement.

metaclass ¶

The class of a class. Class definitions create a class name, a class dictionary, and a list of base classes. The metaclass is responsible for taking those three arguments and creating the class. Most object oriented programming languages provide a default implementation. What makes Python special is that it is possible to create custom metaclasses. Most users never need this tool, but when the need arises, metaclasses can provide powerful, elegant solutions. They have been used for logging attribute access, adding thread-safety, tracking object creation, implementing singletons, and many other tasks.

可以找到更多信息在 元类 .

方法 ¶

A function which is defined inside a class body. If called as an attribute of an instance of that class, the method will get the instance object as its first argument (which is usually called self )。见 function and 嵌套作用域 .

方法分辨次序 ¶

Method Resolution Order is the order in which base classes are searched for a member during lookup. See Python 2.3 MRO (方法分辨次序) for details of the algorithm used by the Python interpreter since the 2.3 release.

模块 ¶

An object that serves as an organizational unit of Python code. Modules have a namespace containing arbitrary Python objects. Modules are loaded into Python by the process of importing .

另请参阅 包 .

模块特定 ¶

包含用于加载模块的导入相关信息的名称空间。实例化的 importlib.machinery.ModuleSpec .

MRO ¶

见 方法分辨次序 .

可变 ¶

可变对象可以改变它们的值但保持它们的 id() 。另请参阅 immutable .

命名元组 ¶

The term “named tuple” applies to any type or class that inherits from tuple and whose indexable elements are also accessible using named attributes. The type or class may have other features as well.

Several built-in types are named tuples, including the values returned by time.localtime() and os.stat() . Another example is sys.float_info :

>>> sys.float_info[1]                   # indexed access
1024
>>> sys.float_info.max_exp              # named field access
1024
>>> isinstance(sys.float_info, tuple)   # kind of tuple
True
						

Some named tuples are built-in types (such as the above examples). Alternatively, a named tuple can be created from a regular class definition that inherits from tuple and that defines named fields. Such a class can be written by hand or it can be created with the factory function collections.namedtuple() . The latter technique also adds some extra methods that may not be found in hand-written or built-in named tuples.

namespace ¶

The place where a variable is stored. Namespaces are implemented as dictionaries. There are the local, global and built-in namespaces as well as nested namespaces in objects (in methods). Namespaces support modularity by preventing naming conflicts. For instance, the functions builtins.open and os.open() are distinguished by their namespaces. Namespaces also aid readability and maintainability by making it clear which module implements a function. For instance, writing random.seed() or itertools.islice() makes it clear that those functions are implemented by the random and itertools modules, respectively.

名称空间包 ¶

A PEP 420 包 which serves only as a container for subpackages. Namespace packages may have no physical representation, and specifically are not like a 正则包 because they have no __init__.py 文件。

另请参阅 module .

嵌套作用域 ¶

The ability to refer to a variable in an enclosing definition. For instance, a function defined inside another function can refer to variables in the outer function. Note that nested scopes by default work only for reference and not for assignment. Local variables both read and write in the innermost scope. Likewise, global variables read and write to the global namespace. The nonlocal allows writing to outer scopes.

新样式类 ¶

Old name for the flavor of classes now used for all class objects. In earlier Python versions, only new-style classes could use Python’s newer, versatile features like __slots__ ，描述符，特性， __getattribute__() ，类方法，和静态方法。

对象 ¶

Any data with state (attributes or value) and defined behavior (methods). Also the ultimate base class of any 新样式类 .

包 ¶

Python module which can contain submodules or recursively, subpackages. Technically, a package is a Python module with an __path__ 属性。

另请参阅 正则包 and 名称空间包 .

参数 ¶

A named entity in a function (or method) definition that specifies an argument (or in some cases, arguments) that the function can accept. There are five kinds of parameter:

• 位置或关键词 : specifies an argument that can be passed either positionally 或作为 关键词自变量 . This is the default kind of parameter, for example foo and bar in the following:

  def func(foo, bar=None): ...
  								

• 仅位置 : specifies an argument that can be supplied only by position. Positional-only parameters can be defined by including a / character in the parameter list of the function definition after them, for example posonly1 and posonly2 in the following:

  def func(posonly1, posonly2, /, positional_or_keyword): ...
  								

• 仅关键词 : specifies an argument that can be supplied only by keyword. Keyword-only parameters can be defined by including a single var-positional parameter or bare * in the parameter list of the function definition before them, for example kw_only1 and kw_only2 in the following:

  def func(arg, *, kw_only1, kw_only2): ...
  								

• var-positional : specifies that an arbitrary sequence of positional arguments can be provided (in addition to any positional arguments already accepted by other parameters). Such a parameter can be defined by prepending the parameter name with * ，例如 args in the following:

  def func(*args, **kwargs): ...
  								

• var-keyword : specifies that arbitrarily many keyword arguments can be provided (in addition to any keyword arguments already accepted by other parameters). Such a parameter can be defined by prepending the parameter name with ** ，例如 kwargs in the example above.

Parameters can specify both optional and required arguments, as well as default values for some optional arguments.

另请参阅 argument 词汇表条目，FAQ 问题有关 自变量和参数之间的差异 ， inspect.Parameter 类， 函数定义 章节，和 PEP 362 .

路径条目 ¶

A single location on the 导入路径 which the 基于路径的查找器 consults to find modules for importing.

路径条目查找器 ¶

A finder returned by a callable on sys.path_hooks (i.e. a 路径条目挂钩 ) which knows how to locate modules given a 路径条目 .

见 importlib.abc.PathEntryFinder for the methods that path entry finders implement.

路径条目挂钩 ¶

A callable on the sys.path_hook list which returns a 路径条目查找器 if it knows how to find modules on a specific 路径条目 .

基于路径的查找器 ¶

One of the default 元路径查找器 which searches an 导入路径 对于模块。

像路径对象 ¶

表示文件系统路径的对象。像路径对象是 str or bytes 对象表示路径，或对象有实现 os.PathLike 协议。对象支持 os.PathLike 协议可以被转换成 str or bytes 文件系统路径通过调用 os.fspath() 函数； os.fsdecode() and os.fsencode() 可以用于保证 str or bytes 代替结果，分别。引入通过 PEP 519 .

PEP ¶

Python Enhancement Proposal. A PEP is a design document providing information to the Python community, or describing a new feature for Python or its processes or environment. PEPs should provide a concise technical specification and a rationale for proposed features.

PEPs are intended to be the primary mechanisms for proposing major new features, for collecting community input on an issue, and for documenting the design decisions that have gone into Python. The PEP author is responsible for building consensus within the community and documenting dissenting opinions.

见 PEP 1 .

portion ¶

A set of files in a single directory (possibly stored in a zip file) that contribute to a namespace package, as defined in PEP 420 .

位置自变量 ¶

见 argument .

provisional API ¶

A provisional API is one which has been deliberately excluded from the standard library’s backwards compatibility guarantees. While major changes to such interfaces are not expected, as long as they are marked provisional, backwards incompatible changes (up to and including removal of the interface) may occur if deemed necessary by core developers. Such changes will not be made gratuitously – they will occur only if serious fundamental flaws are uncovered that were missed prior to the inclusion of the API.

Even for provisional APIs, backwards incompatible changes are seen as a “solution of last resort” - every attempt will still be made to find a backwards compatible resolution to any identified problems.

This process allows the standard library to continue to evolve over time, without locking in problematic design errors for extended periods of time. See PEP 411 了解更多细节。

provisional package ¶

见 provisional API .

Python 3000 ¶

Nickname for the Python 3.x release line (coined long ago when the release of version 3 was something in the distant future.) This is also abbreviated “Py3k”.

Pythonic ¶

An idea or piece of code which closely follows the most common idioms of the Python language, rather than implementing code using concepts common to other languages. For example, a common idiom in Python is to loop over all elements of an iterable using a for statement. Many other languages don’t have this type of construct, so people unfamiliar with Python sometimes use a numerical counter instead:

for i in range(len(food)):
    print(food[i])
						

As opposed to the cleaner, Pythonic method:

for piece in food:
    print(piece)
						

合格名称 ¶

A dotted name showing the “path” from a module’s global scope to a class, function or method defined in that module, as defined in PEP 3155 . For top-level functions and classes, the qualified name is the same as the object’s name:

>>> class C:
...     class D:
...         def meth(self):
...             pass
...
>>> C.__qualname__
'C'
>>> C.D.__qualname__
'C.D'
>>> C.D.meth.__qualname__
'C.D.meth'
						

When used to refer to modules, the fully qualified name means the entire dotted path to the module, including any parent packages, e.g. email.mime.text :

>>> import email.mime.text
>>> email.mime.text.__name__
'email.mime.text'
						

引用计数 ¶

The number of references to an object. When the reference count of an object drops to zero, it is deallocated. Reference counting is generally not visible to Python code, but it is a key element of the CPython implementation. Programmers can call the sys.getrefcount() function to return the reference count for a particular object.

正则包 ¶

A traditional 包 , such as a directory containing an __init__.py 文件。

另请参阅 名称空间包 .

__slots__ ¶

A declaration inside a class that saves memory by pre-declaring space for instance attributes and eliminating instance dictionaries. Though popular, the technique is somewhat tricky to get right and is best reserved for rare cases where there are large numbers of instances in a memory-critical application.

sequence ¶

An iterable which supports efficient element access using integer indices via the __getitem__() special method and defines a __len__() method that returns the length of the sequence. Some built-in sequence types are list , str , tuple ，和 bytes 。注意， dict also supports __getitem__() and __len__() , but is considered a mapping rather than a sequence because the lookups use arbitrary immutable keys rather than integers.

collections.abc.Sequence abstract base class defines a much richer interface that goes beyond just __getitem__() and __len__() ，添加 count() , index() , __contains__() ，和 __reversed__() . Types that implement this expanded interface can be registered explicitly using register() .

set comprehension ¶

A compact way to process all or part of the elements in an iterable and return a set with the results. results = {c for c in 'abracadabra' if c not in 'abc'} generates the set of strings {'r', 'd'} 。见 显示列表、集和字典 .

单次分派 ¶

A form of 一般函数 dispatch where the implementation is chosen based on the type of a single argument.

slice ¶

An object usually containing a portion of a sequence . A slice is created using the subscript notation, [] with colons between numbers when several are given, such as in variable_name[1:3:5] . The bracket (subscript) notation uses slice objects internally.

特殊方法 ¶

A method that is called implicitly by Python to execute a certain operation on a type, such as addition. Such methods have names starting and ending with double underscores. Special methods are documented in 特殊方法名称 .

语句 ¶

A statement is part of a suite (a “block” of code). A statement is either an 表达式 or one of several constructs with a keyword, such as if , while or for .

强引用 ¶

In Python’s C API, a strong reference is a reference to an object which increments the object’s reference count when it is created and decrements the object’s reference count when it is deleted.

Py_NewRef() function can be used to create a strong reference to an object. Usually, the Py_DECREF() function must be called on the strong reference before exiting the scope of the strong reference, to avoid leaking one reference.

另请参阅 借位引用 .

文本编码 ¶

Python 字符串是 Unicode 代码点序列 (在范围 U+0000 – U+10FFFF )。要存储 (或传输) 字符串，需要将它序列化成字节序列。

将字符串序列化成字节序列称为 "编码"，而从字节序列重新创建字符串称为 "解码"。

有各种不同文本序列化 codecs ，统称为 "文本编码"。

文本文件 ¶

文件对象 能读取和写入 str 对象。经常，文本文件实际访问面向字节的数据流，并处理 文本编码 自动。文本文件范例是打开文件按文本模式 ( 'r' or 'w' ), sys.stdin , sys.stdout ，和实例化的 io.StringIO .

另请参阅 二进制文件 为文件对象能读取和写入 像字节对象 .

三引号字符串 ¶

A string which is bound by three instances of either a quotation mark (”) or an apostrophe (‘). While they don’t provide any functionality not available with single-quoted strings, they are useful for a number of reasons. They allow you to include unescaped single and double quotes within a string and they can span multiple lines without the use of the continuation character, making them especially useful when writing docstrings.

type ¶

The type of a Python object determines what kind of object it is; every object has a type. An object’s type is accessible as its __class__ attribute or can be retrieved with type(obj) .

类型别名 ¶

类型的同义词，通过将类型赋值给标识符创建。

类型别名很有用为简化 类型提示 。例如：

def remove_gray_shades(
        colors: list[tuple[int, int, int]]) -> list[tuple[int, int, int]]:
    pass
						

可以像这样变得更可读：

Color = tuple[int, int, int]
def remove_gray_shades(colors: list[Color]) -> list[Color]:
    pass
						

见 typing and PEP 484 ，描述此功能。

类型提示 ¶

annotation that specifies the expected type for a variable, a class attribute, or a function parameter or return value.

Type hints are optional and are not enforced by Python but they are useful to static type analysis tools, and aid IDEs with code completion and refactoring.

Type hints of global variables, class attributes, and functions, but not local variables, can be accessed using typing.get_type_hints() .

见 typing and PEP 484 ，描述此功能。

通用换行符 ¶

A manner of interpreting text streams in which all of the following are recognized as ending a line: the Unix end-of-line convention '\n' ，Windows 约定 '\r\n' , and the old Macintosh convention '\r' 。见 PEP 278 and PEP 3116 ，及 bytes.splitlines() for an additional use.

变量注解 ¶

annotation 对于变量或类属性。

当注解变量或类属性时，赋值是可选的：

class C:
    field: 'annotation'
						

变量注解通常用于 类型提示 ：例如，此变量期望获取 int 值：

count: int = 0
						

变量注解句法的解释在章节 注解赋值语句 .

见 函数注解 , PEP 484 and PEP 526 , which describe this functionality. Also see 注解最佳实践 for best practices on working with annotations.

虚拟环境 ¶

A cooperatively isolated runtime environment that allows Python users and applications to install and upgrade Python distribution packages without interfering with the behaviour of other Python applications running on the same system.

另请参阅 venv .

虚拟机 ¶

A computer defined entirely in software. Python’s virtual machine executes the bytecode 发射通过字节码编译器。

Python 禅宗 ¶

Listing of Python design principles and philosophies that are helpful in understanding and using the language. The listing can be found by typing “ import this ” at the interactive prompt.

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