= Python Collections ABC =

'''`collections.abc`''' is a module that contains '''abstract base classes'''.

An abstract base class can be used as a base class for subclassing. It can also be used with `isinstance()` or `issubclass()` for duck type checking. It can also be used for [[Python/TypeAnnotation|type annotations]].

<<TableOfContents>>

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== AsyncGenerator ==

A subclass of `AsyncIterator`. Implements `asend()` and `athrow()`  methods. Optionally, the `__aiter__()`, `__anext__()`, and `aclose()` methods can be overwritten.

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== AsyncIterable ==

Implements an `__aiter__()` method.

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== AsyncIterator ==

A subclass of `AsyncIterable`. Implements a `__anext__()` method. Optionally, the __aiter__()` method can be overwritten.

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== Awaitable ==

Implements an `__await__()` method.

Note that generator-based coroutines (i.e. `@types.coroutine()`) are awaitable even though they do not have an `__await__()` method. Using `isinstance(obj, collections.abc.Awaitable)` for fail to detect them. Instead use `inspect.isawaitable()`.

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== ByteString ==

A subclass of `Sequence`. Implements `__len__()` and `__getitem__()` methods. Optionally, the `__contains__()`, `__iter__()`, `__reversed__()`, `index()`, and `count()` methods can be overwritten.

In the context of type annotations, `ByteString` represents the types of `bytes`, `bytearray`, and `memoryview` for byte sequences.

Do not use `collections.abc.ByteString` for type annotations. The [[Python/Builtins/Types|built-in]] `bytes` type can be used as a shorthand alias.

{{{
b: bytes = b"abc"
}}}

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== Callable ==

Implements a `__call__()` method.

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== Collection ==

A subclass of `Sized`, `Iterable`, and `Container`. Implements `__len__()`, `__iter__()`, and  `__contains__()` methods.

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== Container ==

Implements a `__contains__()` method.

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== Coroutine ==

A subclass of `Awaitable`. Implements `send()` and `throw()` methods. Optionally, the `close()` method can be overwritten.

Note that generator-based coroutines (i.e. `@types.coroutine()`) are awaitable even though they do not have an `__await__()` method. Using `isinstance(obj, collections.abc.Awaitable)` for fail to detect them. Instead use `inspect.isawaitable()`.

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== Generator ==

A subclass of `Iterator`. Implements `send()` and `throw()` methods. Optionally, the `close(), `__iter__()`, and `__next__()` methods can be overwritten.

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== Hashable ==

Implements a `__hash__()` method.

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== ItemsView ==

A subclass of `MappingView` and `Set`. Optionally, the `__contains__()` and `__iter__()` methods can be overwritten.

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== Iterable ==

Implements an `__iter__()` method.

Note that `isinstance(obj, collections.abc.Iterable)` detects objects that are registered as `Iterable` or that have an `__iter__()` method, but it does not detect objects that iterate with the `__getitem__()` method. The only reliable way to detect an iterable object is `iter(obj)`.

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== Iterator ==

A subclass of `Iterable`. Implements a `__next__()` method. Optionally, the `__iter__()` method can be overwritten.

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== KeysView ==

A subclass of `MappingView` and `Set`. Optionally, the `__contains__()` and `__iter__()` methods can be overwritten.

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== Mapping ==

A subclass of `Collection`. Implements `__len__()`, `__iter__()`, and `__getitem__()` methods. Optionally, the `__contains__()`, `keys()`, `items()`, `values()`, `get()`, `__eq__()`, and `__ne__()` methods can be overwritten.

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== MappingView ==

A subclass of `Sized`. Optionally, the `__len__()` method can be overwritten.

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== MutableMapping ==

A subclass of `Mapping`. Implements `__len__()`, `__iter__()`, `__getitem__()`, `__setitem__()`, and `__delitem__()` methods. Optionally, the `__contains__()`, `keys()`, `items()`, `values()`, `get()`, `__eq__()`, `__ne__()`, `pop()`, `popitem()`, `clear()`, `update()`, and `setdefault()` methods can be overwritten.

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== MutableSequence ==

A subclass of `Sequence`. Implements `__len__()`, `__getitem__()`, `__setitem__()`, `__delitem__()`, and `insert()` methods. Optionally, the `__contains__()`, `__iter__()`, `__reversed__()`, `index()`, `count()`, `append()`, `reverse()`, `extend()`, `pop()`, `remove()`, and `__iadd__()` methods can be overwritten.

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== MutableSet ==

A subclass of `Set`. Implements `__len__()`, `__iter__()`, `__contains__()`, `add()`, and `discard()` methods. Optionally, the `__le__()`, `__lt__()`, `__eq__()`, `__ne__()`, `__gt__()`, `__ge__()`, `__and__()`, `__or__()`, `__sub__()`, `__xor__()`, `isdisjoint()`, `clear()`, `pop()`, `remove()`, `__ior__()`, `__iand__()`, `__ixor__()`, and `__isub__()` methods can be overwritten.

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== Reversible ==

A subclass of `Iterable`. Implements a `__reversed__()` method.

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== Set ==

A subclass of `Collection`. Implements `__len__()`, `__iter__()`, and `__contains__()` methods. Optionally, the `__le__()`, `__lt__()`, `__eq__()`, `__ne__()`, `__gt__()`, `__ge__()`, `__and__()`, `__or__()`, `__sub__()`, `__xor__()`, and `isdisjoint()` methods can be overwritten.

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== Sequence ==

A subclass of `Collection` and `Reversible`. Implements `__len__()` and `__getitem__()` methods. Optionally, the `__contains__()`, `__iter__()`, `__reversed__()`, `index()`, and `count()` methods can be overwritten.

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== Sized ==

Implements a `__len__()` method.

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== ValuesView ==

A subclass of `MappingView` and `Collection`. Optionally, the `__contains__()` and `__iter__()` methods can be overwritten.

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== See also ==

[[https://docs.python.org/3/library/collections.abc.html|Python collections.abc module documentation]]



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