gh-101100: Add a table of class attributes to the "Custom classes" section of the data model docs by AlexWaygood · Pull Request #124480 · python/cpython

>>> print(int.__subclasses__())
[<class 'bool'>, <enum 'IntEnum'>, <flag 'IntFlag'>, <class 're._constants._NamedIntConstant'>, <class 're._ZeroSentinel'>]
>>> import enum
>>> def f():
...     class MyIntEnum(int, enum.Enum): pass
...     
>>> f()
>>> print(int.__subclasses__())
[<class 'bool'>, <enum 'IntEnum'>, <flag 'IntFlag'>, <class 're._constants._NamedIntConstant'>, <class 're._ZeroSentinel'>, <enum 'MyIntEnum'>]
>>> import gc
>>> gc.collect()
31
>>> print(int.__subclasses__())
[<class 'bool'>, <enum 'IntEnum'>, <flag 'IntFlag'>, <class 're._constants._NamedIntConstant'>, <class 're._ZeroSentinel'>]
>>>