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[doc] bpo-45680: Disambiguate __getitem__ and __class_getitem__ in the data model. #29389

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ambv merged 11 commits into from
Nov 18, 2021
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[doc] bpo-45680: Disambiguate __getitem__ and __class_getitem__ in the data model. #29389

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[doc] bpo-45680: Disambiguate ``__getitem__`` and ``__class_getitem__…
AlexWaygood Nov 3, 2021
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Update 2021-11-03-14-30-55.bpo-45680.UBpWzY.rst
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@AlexWaygood
AlexWaygood authored Nov 8, 2021
commit c1955d7faf533388d45718dab6e0b8d3d3922784
8 changes: 6 additions & 2 deletions Doc/reference/datamodel.rst
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Expand Up @@ -2282,17 +2282,21 @@ follows something like the following process to decide whether
:meth:`~object.__getitem__` or :meth:`~object.__class_getitem__` should be
called::

from inspect import isclass

def subscribe(obj, x):
"""Return the result of the expression `obj[x]`"""

class_of_obj = type(obj)

# If the class of `obj` defines `__getitem__()`,
# call `type(obj).__getitem__()`
if hasattr(class_of_obj, '__getitem__'):
return class_of_obj.__getitem__(obj, x)

# Else, if `obj` defines `__class_getitem__()`,
# Else, if `obj` is a class and defines `__class_getitem__()`,
# call `obj.__class_getitem__()`
elif hasattr(obj, '__class_getitem__'):
elif isclass(obj) and hasattr(obj, '__class_getitem__'):
return obj.__class_getitem__(x)

# Else, raise an exception
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