Bug report

Bug description:

Metaclass __call__ is expected to run everytime a class is instantiated but in Python 3.13 it only run once.

Minimal reproducer:

class _TypeMetaclass(type): def __call__(cls, *args, **kwargs): print("Metaclass.__call__", cls.__qualname__, args) inst = type.__call__(cls, *args, **kwargs) return inst class Type(metaclass=_TypeMetaclass): def __init__(self, obj): self._obj = obj class Function(Type): pass for i in range(100): Function(i)

On python 3.12, the output is:

Metaclass.__call__ Function (0,) Metaclass.__call__ Function (1,) Metaclass.__call__ Function (2,) ... Metaclass.__call__ Function (98,) Metaclass.__call__ Function (99,) 

On python 3.13 (docker image 3.13.0a3-bullseye), the output is unexpectedly:

Metaclass.__call__ Function (0,) 

CPython versions tested on:

3.12, 3.13

Operating systems tested on:

Linux

Linked PRs

• GH-114806. Don't specialize calls to classes with metaclasses. #114870