"collections.abc" --- Classes Base Abstratas para Contêineres
*************************************************************

Adicionado na versão 3.3: Anteriormente, esse módulo fazia parte do
módulo "collections".

**Código-fonte:** Lib/_collections_abc.py

======================================================================

Esse módulo fornece *classes base abstratas* que podem ser usadas para
testar se uma classe fornece uma interface específica; por exemplo, se
é *hasheável* ou se é um *mapeamento*.

Um teste "issubclass()" ou "isinstance()" para uma interface funciona
em uma das três formas.

1) A newly written class can inherit directly from one of the abstract
base classes.  The class must supply the required abstract methods.
The remaining mixin methods come from inheritance and can be
overridden if desired.  Other methods may be added as needed:

   class C(Sequence):                      # Herança direta
       def __init__(self): ...             # Método extra não exigido pela ABC
       def __getitem__(self, index):  ...  # Método abstrato exigido
       def __len__(self):  ...             # Método abstrato exigido
       def count(self, value): ...         # Opcionalmente substitui um método mixin

   >>> issubclass(C, Sequence)
   True
   >>> isinstance(C(), Sequence)
   True

2) Existing classes and built-in classes can be registered as "virtual
subclasses" of the ABCs.  Those classes should define the full API
including all of the abstract methods and all of the mixin methods.
This lets users rely on "issubclass()" or "isinstance()" tests to
determine whether the full interface is supported.  The exception to
this rule is for methods that are automatically inferred from the rest
of the API:

   class D:                                 # Sem herança
       def __init__(self): ...              # Método extra exigido pela ABC
       def __getitem__(self, index):  ...   # Método abstrato
       def __len__(self):  ...              # Método abstrato
       def count(self, value): ...          # Método mixin
       def index(self, value): ...          # Método mixin

   Sequence.register(D)                     # Registra ao invés de herdar

   >>> issubclass(D, Sequence)
   True
   >>> isinstance(D(), Sequence)
   True

In this example, class "D" does not need to define "__contains__",
"__iter__", and "__reversed__" because the in-operator, the
*iteration* logic, and the "reversed()" function automatically fall
back to using "__getitem__" and "__len__".

3) Some simple interfaces are directly recognizable by the presence of
the required methods (unless those methods have been set to "None"):

   class E:
       def __iter__(self): ...
       def __next__(self): ...

   >>> issubclass(E, Iterable)
   True
   >>> isinstance(E(), Iterable)
   True

Complex interfaces do not support this last technique because an
interface is more than just the presence of method names.  Interfaces
specify semantics and relationships between methods that cannot be
inferred solely from the presence of specific method names.  For
example, knowing that a class supplies "__getitem__", "__len__", and
"__iter__" is insufficient for distinguishing a "Sequence" from a
"Mapping".

Adicionado na versão 3.9: These abstract classes now support "[]". See
Tipo Generic Alias and **PEP 585**.


Classes Base Abstratas de Coleções
==================================

O módulo de coleções oferece o seguinte *ABCs*:

+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| ABC                            | Herda de               | Métodos Abstratos       | Métodos Mixin                                        |
|================================|========================|=========================|======================================================|
| "Container" [1]                |                        | "__contains__"          |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Hashable" [1]                 |                        | "__hash__"              |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Iterable" [1] [2]             |                        | "__iter__"              |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Iterator" [1]                 | "Iterable"             | "__next__"              | "__iter__"                                           |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Reversible" [1]               | "Iterable"             | "__reversed__"          |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Generator"  [1]               | "Iterator"             | "send", "throw"         | "close", "__iter__", "__next__"                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Sized"  [1]                   |                        | "__len__"               |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Callable"  [1]                |                        | "__call__"              |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Collection"  [1]              | "Sized", "Iterable",   | "__contains__",         |                                                      |
|                                | "Container"            | "__iter__", "__len__"   |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Sequence"                     | "Reversible",          | "__getitem__",          | "__contains__", "__iter__", "__reversed__", "index", |
|                                | "Collection"           | "__len__"               | and "count"                                          |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "MutableSequence"              | "Sequence"             | "__getitem__",          | Inherited "Sequence" methods and "append", "clear",  |
|                                |                        | "__setitem__",          | "reverse", "extend", "pop", "remove", and "__iadd__" |
|                                |                        | "__delitem__",          |                                                      |
|                                |                        | "__len__", "insert"     |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "ByteString"                   | "Sequence"             | "__getitem__",          | Herdado "Sequence" métodos                           |
|                                |                        | "__len__"               |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Set"                          | "Collection"           | "__contains__",         | "__le__", "__lt__", "__eq__", "__ne__", "__gt__",    |
|                                |                        | "__iter__", "__len__"   | "__ge__", "__and__", "__or__", "__sub__", "__xor__", |
|                                |                        |                         | e "isdisjoint"                                       |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "MutableSet"                   | "Set"                  | "__contains__",         | Herdado "Set" métodos e "clear", "pop", "remove",    |
|                                |                        | "__iter__", "__len__",  | "__ior__", "__iand__", "__ixor__", e "__isub__"      |
|                                |                        | "add", "discard"        |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Mapping"                      | "Collection"           | "__getitem__",          | "__contains__", "keys", "items", "values", "get",    |
|                                |                        | "__iter__", "__len__"   | "__eq__", e "__ne__"                                 |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "MutableMapping"               | "Mapping"              | "__getitem__",          | Herdado "Mapping" métodos e "pop", "popitem",        |
|                                |                        | "__setitem__",          | "clear", "update", e "setdefault"                    |
|                                |                        | "__delitem__",          |                                                      |
|                                |                        | "__iter__", "__len__"   |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "MappingView"                  | "Sized"                |                         | "__len__"                                            |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "ItemsView"                    | "MappingView", "Set"   |                         | "__contains__", "__iter__"                           |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "KeysView"                     | "MappingView", "Set"   |                         | "__contains__", "__iter__"                           |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "ValuesView"                   | "MappingView",         |                         | "__contains__", "__iter__"                           |
|                                | "Collection"           |                         |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Awaitable" [1]                |                        | "__await__"             |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Coroutine" [1]                | "Awaitable"            | "send", "throw"         | "close"                                              |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "AsyncIterable" [1]            |                        | "__aiter__"             |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "AsyncIterator" [1]            | "AsyncIterable"        | "__anext__"             | "__aiter__"                                          |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "AsyncGenerator" [1]           | "AsyncIterator"        | "asend", "athrow"       | "aclose", "__aiter__", "__anext__"                   |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+
| "Buffer" [1]                   |                        | "__buffer__"            |                                                      |
+--------------------------------+------------------------+-------------------------+------------------------------------------------------+

-[ Notas de rodapé ]-

[1] These ABCs override "__subclasshook__()" to support testing an
    interface by verifying the required methods are present and have
    not been set to "None".  This only works for simple interfaces.
    More complex interfaces require registration or direct
    subclassing.

[2] 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* is to call "iter(obj)".


Collections Abstract Base Classes -- Detailed Descriptions
==========================================================

class collections.abc.Container

   ABC for classes that provide the "__contains__()" method.

class collections.abc.Hashable

   ABC for classes that provide the "__hash__()" method.

class collections.abc.Sized

   ABC for classes that provide the "__len__()" method.

class collections.abc.Callable

   ABC for classes that provide the "__call__()" method.

   See Anotações de objetos chamáveis for details on how to use
   "Callable" in type annotations.

class collections.abc.Iterable

   ABC for classes that provide the "__iter__()" method.

   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* is to call "iter(obj)".

class collections.abc.Collection

   ABC para classes de contêiner iterável de tamanho.

   Adicionado na versão 3.6.

class collections.abc.Iterator

   ABC para classes que fornecem os métodos "__iter__()" e métodos
   "__next__()". Veja também a definição de *iterator*.

class collections.abc.Reversible

   ABC for iterable classes that also provide the "__reversed__()"
   method.

   Adicionado na versão 3.6.

class collections.abc.Generator

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

   See Annotating generators and coroutines for details on using
   "Generator" in type annotations.

   Adicionado na versão 3.5.

class collections.abc.Sequence
class collections.abc.MutableSequence
class collections.abc.ByteString

   ABCs para *sequências* somente de leitura e mutáveis.

   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.

   Alterado na versão 3.5: O método index() adicionou suporte para os
   argumentos *stop* e *start*.

   Deprecated since version 3.12, will be removed in version 3.14: The
   "ByteString" ABC has been deprecated. For use in typing, prefer a
   union, like "bytes | bytearray", or "collections.abc.Buffer". For
   use as an ABC, prefer "Sequence" or "collections.abc.Buffer".

class collections.abc.Set
class collections.abc.MutableSet

   ABCs for read-only and mutable sets.

class collections.abc.Mapping
class collections.abc.MutableMapping

   ABCs para somente leitura e mutável *mappings*.

class collections.abc.MappingView
class collections.abc.ItemsView
class collections.abc.KeysView
class collections.abc.ValuesView

   ABCs para mapeamento, itens, chaves e valores *views*.

class collections.abc.Awaitable

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

   Objetos e instâncias de *corrotina* da ABC "Coroutine" são todas
   instâncias dessa ABC.

   Nota:

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

   Adicionado na versão 3.5.

class collections.abc.Coroutine

   ABC for *coroutine* compatible classes.  These implement the
   following methods, defined in Objetos corrotina: "send()",
   "throw()", and "close()".  Custom implementations must also
   implement "__await__()".  All "Coroutine" instances are also
   instances of "Awaitable".

   Nota:

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

   See Annotating generators and coroutines for details on using
   "Coroutine" in type annotations. The variance and order of type
   parameters correspond to those of "Generator".

   Adicionado na versão 3.5.

class collections.abc.AsyncIterable

   ABC for classes that provide an "__aiter__" method.  See also the
   definition of *asynchronous iterable*.

   Adicionado na versão 3.5.

class collections.abc.AsyncIterator

   ABC para classes que fornecem os métodos "__aiter__" e "__anext__".
   Veja também a definição de *iterador assíncrono*.

   Adicionado na versão 3.5.

class collections.abc.AsyncGenerator

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

   See Annotating generators and coroutines for details on using
   "AsyncGenerator" in type annotations.

   Adicionado na versão 3.6.

class collections.abc.Buffer

   ABC for classes that provide the "__buffer__()" method,
   implementing the buffer protocol. See **PEP 688**.

   Adicionado na versão 3.12.


Exemplos e receitas
===================

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__()",
and "__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

Notas sobre o uso de "Set" e "MutableSet" como um 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()" which calls
   "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 or regular
   method 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".

Ver também:

  * OrderedSet receita para um exemplo baseado em "MutableSet".

  * Para mais informações sobre ABCs, consulte o módulo "abc" e **PEP
    3119**.
