[doc] bpo-45680: Disambiguate __getitem__ and __class_getitem__ in the data model.
#29389
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…`` in the data model. The documentation explaining Python's data model does not adequately explain the differences between ``__getitem__`` and ``__class_getitem__``, nor does it explain when each is called. There is an attempt at explaining ``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but this does not give sufficient clarity into how the method works. Moreover, it is the wrong place for that information to be found; the explanation of ``__class_getitem__`` should be in the documentation explaining the data model. This PR has been split off from python#29335.
AlexWaygood
changed the title
__class_getitem__ in the data model.__getitem__ and __class_getitem__ in the data model.
Thank you <3 |
Massive thanks for the detailed review! I've rewritten large chunks in response (Wow, writing documentation is hard!) |
AlexWaygood
reviewed
Nov 7, 2021
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| Usually, the :ref:`subscription<subscriptions>` of an object using square | ||
| brackets will call the :meth:`~object.__getitem__` instance method defined on | ||
| the object's class. However, if the object being subscribed is itself a class, |
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Should it be "object being subscribed", or "object being subscripted"?
Doc/reference/datamodel.rst
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| def subscribe(obj, x): | ||
| class_of_obj = type(obj) | ||
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| # If the class of `obj` defines `__getitem__()`, | ||
| # call `type(obj).__getitem__()` | ||
| if hasattr(class_of_obj, '__getitem__'): | ||
| return class_of_obj.__getitem__(obj, x) | ||
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| # Else, if `obj` defines `__class_getitem__()`, | ||
| # call `obj.__class_getitem__()` | ||
| elif hasattr(obj, '__class_getitem__'): | ||
| return obj.__class_getitem__(x) | ||
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| # Else, raise an exception | ||
| else: | ||
| raise TypeError( | ||
| f"'{class_of_obj.__name__}' object is not subscriptable" | ||
| ) |
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Please correct me if this isn't quite right -- I'm in a little over my head here!
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Okay, the CI failures are because |
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Thanks @AlexWaygood for the PR, and @ambv for merging it |
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Thanks @AlexWaygood for the PR, and @ambv for merging it |
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GH-29619 is a backport of this pull request to the 3.9 branch. |
miss-islington
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Nov 18, 2021
…`` in the data model (pythonGH-29389) The documentation explaining Python's data model does not adequately explain the differences between ``__getitem__`` and ``__class_getitem__``, nor does it explain when each is called. There is an attempt at explaining ``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but this does not give sufficient clarity into how the method works. Moreover, it is the wrong place for that information to be found; the explanation of ``__class_getitem__`` should be in the documentation explaining the data model. This PR has been split off from pythonGH-29335. (cherry picked from commit 31b3a70) Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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GH-29620 is a backport of this pull request to the 3.10 branch. |
miss-islington
added a commit
to miss-islington/cpython
that referenced
this issue
Nov 18, 2021
…`` in the data model (pythonGH-29389) The documentation explaining Python's data model does not adequately explain the differences between ``__getitem__`` and ``__class_getitem__``, nor does it explain when each is called. There is an attempt at explaining ``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but this does not give sufficient clarity into how the method works. Moreover, it is the wrong place for that information to be found; the explanation of ``__class_getitem__`` should be in the documentation explaining the data model. This PR has been split off from pythonGH-29335. (cherry picked from commit 31b3a70) Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
ambv
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Nov 18, 2021
…titem__`` in the data model (GH-29389) (GH-29620) The documentation explaining Python's data model does not adequately explain the differences between ``__getitem__`` and ``__class_getitem__``, nor does it explain when each is called. There is an attempt at explaining ``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but this does not give sufficient clarity into how the method works. Moreover, it is the wrong place for that information to be found; the explanation of ``__class_getitem__`` should be in the documentation explaining the data model. This PR has been split off from GH-29335. (cherry picked from commit 31b3a70) Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com> Co-authored-by: Łukasz Langa <lukasz@langa.pl>
ambv
added a commit
that referenced
this issue
Nov 18, 2021
…item__`` in the data model (GH-29389) (GH-29619) The documentation explaining Python's data model does not adequately explain the differences between ``__getitem__`` and ``__class_getitem__``, nor does it explain when each is called. There is an attempt at explaining ``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but this does not give sufficient clarity into how the method works. Moreover, it is the wrong place for that information to be found; the explanation of ``__class_getitem__`` should be in the documentation explaining the data model. This PR has been split off from GH-29335. (cherry picked from commit 31b3a70) Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com> Co-authored-by: Łukasz Langa <lukasz@langa.pl>
remykarem
added a commit
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that referenced
this issue
Dec 7, 2021
…`` in the data model (pythonGH-29389) The documentation explaining Python's data model does not adequately explain the differences between ``__getitem__`` and ``__class_getitem__``, nor does it explain when each is called. There is an attempt at explaining ``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but this does not give sufficient clarity into how the method works. Moreover, it is the wrong place for that information to be found; the explanation of ``__class_getitem__`` should be in the documentation explaining the data model. This PR has been split off from pythonGH-29335.
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The documentation explaining Python's data model does not adequately explain
the differences between
__getitem__and__class_getitem__, nor does itexplain when each is called. There is an attempt at explaining
__class_getitem__in the documentation forGenericAliasobjects, butthis does not give sufficient clarity into how the method works. Moreover, it
is the wrong place for that information to be found; the explanation of
__class_getitem__should be in the documentation explaining the data model.This PR has been split off from #29335.
https://bugs.python.org/issue45680
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