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Description
Instances oftypes.GenericAlias are accepted as the first argument ofissubclass():
>>>issubclass(list[int],object)True>>>issubclass(list[int],type)False
while instances oftyping.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 class
Although 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 class
Usuallyissubclass(x, y) is preceded by the checkisinstance(x, type), so the final result will always be false since 3.11, but if that check is omitted, you can see a difference.