Allow object.__init_subclass__ to take keyword arguments

[Melendowski (Matt D)]

Is the problem described by OP the cause of my error in this post of mine?

Required kwarg in __prepare__

Hi I am attempt to learn the class creation process better. I am interested in the aspect of class parameterization. Why do I get an error if I make a required key word argument in __prepare__? If I just use the default value, the class is defined properly but if i explicitly pass it, I get an error in __init_subclass__? In [13]: class Meta(type): ...: @classmethod ...: def __prepare__(mcs, *args, required_kwarg="foo", **kwargs): ...: print(required_kwarg) ...: …

Specifically, the fact that object.__init_subclass__ does not take arbitrary kwargs, causes issues when passing class parametrizations to __prepare__, which invariably get funneled directly to __init_subclass__ for some reason?

PEP 3115 introduces the ability to parametrize classes, and then PEP487 shows extended use cases by being able to pass keywords to __init_subclass__ through that mechanism.