Closed
Description
Instances of types.GenericAlias are accepted as the first argument of issubclass():
>>> issubclass(list[int], object) True >>> issubclass(list[int], type) Falsewhile instances of typing.GenericAlias are not:
>>> issubclass(typing.List[int], object) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: issubclass() arg 1 must be a class >>> issubclass(typing.List[int], type) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: issubclass() arg 1 must be a classAlthough both are rejected if the second argument is an abstract class:
>>> issubclass(list[int], collections.abc.Sequence) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/home/serhiy/py/cpython/Lib/abc.py", line 123, in __subclasscheck__ return _abc_subclasscheck(cls, subclass) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TypeError: issubclass() arg 1 must be a class >>> issubclass(typing.List[int], collections.abc.Sequence) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/home/serhiy/py/cpython/Lib/abc.py", line 123, in __subclasscheck__ return _abc_subclasscheck(cls, subclass) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TypeError: issubclass() arg 1 must be a classUsually issubclass(x, y) is preceded by the check isinstance(x, type), so the final result will always be false since 3.11, but if that check is omitted, you can see a difference.