collections.abc — 容器抽象基类 ¶

3.3 版新增： Formerly, this module was part of the collections 模块。

源代码： Lib/_collections_abc.py

---

本模块提供 抽象基类 that can be used to test whether a class provides a particular interface; for example, whether it is hashable or whether it is a mapping.

集合抽象基类 ¶

The collections module offers the following ABCs :

ABC (抽象基类)	Inherits from	Abstract Methods	Mixin Methods
Container		__contains__
Hashable		__hash__
Iterable		__iter__
Iterator	Iterable	__next__	__iter__
Reversible	Iterable	__reversed__
Generator	Iterator	send , throw	close , __iter__ , __next__
Sized		__len__
Callable		__call__
Collection	Sized , Iterable , Container	__contains__ , __iter__ , __len__
Sequence	Reversible , Collection	__getitem__ , __len__	__contains__ , __iter__ , __reversed__ , index ，和 count
MutableSequence	Sequence	__getitem__ , __setitem__ , __delitem__ , __len__ , insert	继承 Sequence methods and append , reverse , extend , pop , remove ，和 __iadd__
ByteString	Sequence	__getitem__ , __len__	继承 Sequence 方法
Set	Collection	__contains__ , __iter__ , __len__	__le__ , __lt__ , __eq__ , __ne__ , __gt__ , __ge__ , __and__ , __or__ , __sub__ , __xor__ ，和 isdisjoint
MutableSet	Set	__contains__ , __iter__ , __len__ , add , discard	继承 Set methods and clear , pop , remove , __ior__ , __iand__ , __ixor__ ，和 __isub__
Mapping	Collection	__getitem__ , __iter__ , __len__	__contains__ , keys , items , values , get , __eq__ ，和 __ne__
MutableMapping	Mapping	__getitem__ , __setitem__ , __delitem__ , __iter__ , __len__	继承 Mapping methods and pop , popitem , clear , update ，和 setdefault
MappingView	Sized		__len__
ItemsView	MappingView , Set		__contains__ , __iter__
KeysView	MappingView , Set		__contains__ , __iter__
ValuesView	MappingView , Collection		__contains__ , __iter__
Awaitable		__await__
Coroutine	Awaitable	send , throw	close
AsyncIterable		__aiter__
AsyncIterator	AsyncIterable	__anext__	__aiter__
AsyncGenerator	AsyncIterator	asend , athrow	aclose , __aiter__ , __anext__

class collections.abc. Container ¶

ABC for classes that provide the __contains__() 方法。

class collections.abc. Hashable ¶

ABC for classes that provide the __hash__() 方法。

class collections.abc. Sized ¶

ABC for classes that provide the __len__() 方法。

class collections.abc. 可调用 ¶

ABC for classes that provide the __call__() 方法。

class collections.abc. Iterable ¶

ABC for classes that provide the __iter__() 方法。

Checking isinstance(obj, Iterable) detects classes that are registered as Iterable or that have an __iter__() method, but it does not detect classes that iterate with the __getitem__() method. The only reliable way to determine whether an object is iterable 是调用 iter(obj) .

class collections.abc. Collection ¶

ABC for sized iterable container classes.

3.6 版新增。

class collections.abc. 迭代器 ¶

ABC for classes that provide the __iter__() and __next__() methods. See also the definition of iterator .

class collections.abc. Reversible ¶

ABC for iterable classes that also provide the __reversed__() 方法。

3.6 版新增。

class collections.abc. 生成器 ¶

ABC for generator classes that implement the protocol defined in PEP 342 that extends iterators with the send() , throw() and close() methods. See also the definition of generator .

3.5 版新增。

class collections.abc. Sequence ¶

class collections.abc. MutableSequence ¶

class collections.abc. ByteString ¶

ABCs for read-only and mutable sequences .

Implementation note: Some of the mixin methods, such as __iter__() , __reversed__() and index() , make repeated calls to the underlying __getitem__() method. Consequently, if __getitem__() is implemented with constant access speed, the mixin methods will have linear performance; however, if the underlying method is linear (as it would be with a linked list), the mixins will have quadratic performance and will likely need to be overridden.

3.5 版改变： The index() method added support for stop and start 自变量。

class collections.abc. Set ¶

class collections.abc. MutableSet ¶

ABCs for read-only and mutable sets.

class collections.abc. 映射 ¶

class collections.abc. MutableMapping ¶

ABCs for read-only and mutable mappings .

class collections.abc. MappingView ¶

class collections.abc. ItemsView ¶

class collections.abc. KeysView ¶

class collections.abc. ValuesView ¶

ABCs for mapping, items, keys, and values views .

class collections.abc. Awaitable ¶

ABC for awaitable objects, which can be used in await expressions. Custom implementations must provide the __await__() 方法。

Coroutine objects and instances of the Coroutine ABC are all instances of this ABC.

注意

In CPython, generator-based coroutines (generators decorated with types.coroutine() or asyncio.coroutine() ) are awaitables , even though they do not have an __await__() method. Using isinstance(gencoro, Awaitable) for them will return False 。使用 inspect.isawaitable() to detect them.

3.5 版新增。

class collections.abc. Coroutine ¶

ABC for coroutine compatible classes. These implement the following methods, defined in 协程对象 : send() , throw() ，和 close() . Custom implementations must also implement __await__() . All Coroutine instances are also instances of Awaitable 。另请参阅定义对于 协程 .

注意

In CPython, generator-based coroutines (generators decorated with types.coroutine() or asyncio.coroutine() ) are awaitables , even though they do not have an __await__() method. Using isinstance(gencoro, Coroutine) for them will return False 。使用 inspect.isawaitable() to detect them.

3.5 版新增。

class collections.abc. AsyncIterable ¶

ABC for classes that provide __aiter__ method. See also the definition of 异步可迭代 .

3.5 版新增。

class collections.abc. AsyncIterator ¶

ABC for classes that provide __aiter__ and __anext__ methods. See also the definition of 异步迭代器 .

3.5 版新增。

class collections.abc. AsyncGenerator ¶

ABC for asynchronous generator classes that implement the protocol defined in PEP 525 and PEP 492 .

3.6 版新增。

These ABCs allow us to ask classes or instances if they provide particular functionality, for example:

size = None
if isinstance(myvar, collections.abc.Sized):
    size = len(myvar)
						

Several of the ABCs are also useful as mixins that make it easier to develop classes supporting container APIs. For example, to write a class supporting the full Set API, it is only necessary to supply the three underlying abstract methods: __contains__() , __iter__() ，和 __len__() . The ABC supplies the remaining methods such as __and__() and isdisjoint() :

class ListBasedSet(collections.abc.Set):
    ''' Alternate set implementation favoring space over speed
        and not requiring the set elements to be hashable. '''
    def __init__(self, iterable):
        self.elements = lst = []
        for value in iterable:
            if value not in lst:
                lst.append(value)
    def __iter__(self):
        return iter(self.elements)
    def __contains__(self, value):
        return value in self.elements
    def __len__(self):
        return len(self.elements)
s1 = ListBasedSet('abcdef')
s2 = ListBasedSet('defghi')
overlap = s1 & s2            # The __and__() method is supported automatically
						

Notes on using Set and MutableSet as a mixin:

1. Since some set operations create new sets, the default mixin methods need a way to create new instances from an iterable. The class constructor is assumed to have a signature in the form ClassName(iterable) . That assumption is factored-out to an internal classmethod called _from_iterable() 调用 cls(iterable) to produce a new set. If the Set mixin is being used in a class with a different constructor signature, you will need to override _from_iterable() with a classmethod that can construct new instances from an iterable argument.

2. To override the comparisons (presumably for speed, as the semantics are fixed), redefine __le__() and __ge__() , then the other operations will automatically follow suit.

3. The Set mixin provides a _hash() method to compute a hash value for the set; however, __hash__() is not defined because not all sets are hashable or immutable. To add set hashability using mixins, inherit from both Set() and Hashable() , then define __hash__ = Set._hash .

另请参阅

• OrderedSet recipe for an example built on MutableSet .

• For more about ABCs, see the abc module and PEP 3119 .

内容表

• collections.abc — 容器抽象基类
  • 集合抽象基类

上一话题

collections — 容器数据类型

下一话题

heapq — 堆队列算法

本页

• 报告 Bug
• 展示源