specify metaclass for dynamic type

Question

In Python, you can create types dynamically using the function my_type = type(name, bases, dict). How would you specify a metaclass for this type my_type? (Ideally other than defining a throwaway class object that simply binds the metaclass to instantiated subclasses)

Answer 1

For Dynamic Type Creation where you need to provide keywords in the class statement (including, but not limited to, the keyword "metaclass"), you would use types.new_class. The following class definition:

class A(B, C, metaclass=AMeta):
    pass

Can be created dynamically like:

A = types.new_class(
    name="A",
    bases=(B, C),
    kwds={"metaclass": AMeta},
    exec_body=None,
)

This is preferable to directly calling type, or any other metaclass, since it resolves the metaclass bases - depending on the types of B and C, the type(A) here might not necessarily be AMeta.