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bpo-42010: [docs] Clarify subscription of types (GH-22822)
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@ -800,8 +800,8 @@ Subscriptions
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object: dictionary
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object: dictionary
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pair: sequence; item
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pair: sequence; item
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A subscription selects an item of a sequence (string, tuple or list) or mapping
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Subscription of a sequence (string, tuple or list) or mapping (dictionary)
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(dictionary) object:
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object usually selects an item from the collection:
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.. productionlist:: python-grammar
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.. productionlist:: python-grammar
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subscription: `primary` "[" `expression_list` "]"
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subscription: `primary` "[" `expression_list` "]"
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@ -837,6 +837,17 @@ this method will need to explicitly add that support.
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A string's items are characters. A character is not a separate data type but a
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A string's items are characters. A character is not a separate data type but a
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string of exactly one character.
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string of exactly one character.
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..
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At the time of writing this, there is no documentation for generic alias
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or PEP 585. Thus the link currently points to PEP 585 itself.
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Please change the link for generic alias to reference the correct
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documentation once documentation for PEP 585 becomes available.
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Subscription of certain :term:`classes <class>` or :term:`types <type>`
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creates a `generic alias <https://www.python.org/dev/peps/pep-0585/>`_.
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In this case, user-defined classes can support subscription by providing a
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:meth:`__class_getitem__` classmethod.
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.. _slicings:
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.. _slicings:
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@ -0,0 +1,4 @@
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Clarify that subscription expressions are also valid for certain
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:term:`classes <class>` and :term:`types <type>` in the standard library, and
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for user-defined classes and types if the classmethod
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:meth:`__class_getitem__` is provided.
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