> As a matter of fact, A.__module__ in this case is abc.ABCMeta.__module__. A class body creates a __module__ key, while a direct metaclass call does not.

But

>>> A = ABCMeta('A', (), {})
>>> ABCMeta.__module__ = 'hi'
>>> A.__module__
'abc'
>>> ABCMeta.__module__
'hi'

This means that the __module__ is copied from metaclass (also A.__dict__ actually contains '__module__' key, checked in 3.6).