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Add __class_getitem__ support to ctypes.py_object #132168
Description
Feature or enhancement
Proposal:
ctypes.py_object is generic in typeshed, but is not subscriptable at runtime. This can be troublesome for end users, since type checkers will prompt them to supply a generic type argument, but doing so will produce a TypeError at runtime:
>>> import ctypes
>>> ctypes.py_object[int]
Traceback (most recent call last):
File "<python-input-1>", line 1, in <module>
ctypes.py_object[int]
~~~~~~~~~~~~~~~~^^^^^
TypeError: type 'py_object' is not subscriptable(albeit this is partially mitigated by deferred annotations in 3.14, but TypeError can still pop up if the annotations are ever evaluated)
py_object's typeshed stubs have been stable for a while, and it seems unlikely to be made non-generic in the future. Therefore I propose that __class_getitem__ be added to ctypes.py_object so that it can be subscripted at runtime.
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Activity
picnixz commentedon Apr 6, 2025
What's the reason for having
ctypes.py_objectgeneric actually? what doesctypes.py_object[int]means? does it mean aPyLongObject?sobolevn commentedon Apr 6, 2025
@picnixz see https://github.com/python/typeshed/blob/2b7019b933ac8339e4ae8f4619a2a746446a8532/stdlib/ctypes/__init__.pyi#L253
brianschubert commentedon Apr 6, 2025
It represents a pointer to an arbitrary Python object. Having it be generic lets you statically track the type of that object. I haven't written enough
ctypescode to personally need it, but I imagine it being generic is useful if you need to accesspy_object.value, or if you need to type-hint a function whose behavior depends on the type of object thatpy_objectis holding. It being generic also seems to be useful to numpy.gh-132168: Add `__class_getitem__` to `ctypes.py_object` (#132169)