bpo-32717: Document PEP 560 (GH-6726) · python/cpython@101d0d5 (original) (raw)

`@@ -1857,11 +1857,27 @@ passed through to all metaclass operations described below.

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`When a class definition is executed, the following steps occur:

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`* the appropriate metaclass is determined

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`* the class namespace is prepared

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`* the class body is executed

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`* the class object is created

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Resolving MRO entries

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^^^^^^^^^^^^^^^^^^^^^

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If a base that appears in class definition is not an instance of :class:type,

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then an ``__mro_entries__`` method is searched on it. If found, it is called

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with the original bases tuple. This method must return a tuple of classes that

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will be used instead of this base. The tuple may be empty, in such case

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the original base is ignored.

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.. seealso::

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:pep:560 - Core support for typing module and generic types

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`Determining the appropriate metaclass

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`^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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`.. index::

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` module) to the language.

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Emulating generic types

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One can implement the generic class syntax as specified by :pep:484

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(for example ``List[int]``) by defining a special method

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.. classmethod:: object.class_getitem(cls, key)

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Return an object representing the specialization of a generic class

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by type arguments found in key.

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This method is looked up on the class object itself, and when defined in

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the class body, this method is implicitly a class method. Note, this

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mechanism is primarily reserved for use with static type hints, other usage

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is discouraged.

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.. seealso::

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:pep:560 - Core support for typing module and generic types

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`.. _callable-types:

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`Emulating callable objects

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