class Atype(type):

    def __new__(cls, name, bases, attrs):
        return super(Atype, cls).__new__(cls, name, (Aclass,) + bases, attrs)

def __init__(cls, name, bases, attrs):

    def simple(self, a):
        return cls.complex(self, a, 1)
setattr(cls, 'simple', simple)
Create instance method in metaclass using partial in Python 3