Ensure super __init__ is called

ensure_init.py

def ensure_init(cls):
    def __new__(cls, *args, **kwargs):
        def magic_init(self):
            self.__class__ = cls
            self.__init__(*args, **kwargs)
            if not self.__ensure_init:
                raise TypeError('super __init__ not called')

        # magic to use custom init while pretending a cls instance
        t = type('', (cls,), {'__init__': magic_init})
        return object.__new__(t)

    init = cls.__init__  # cls.__init__ will be rebound!

    def __init__(self, *args, **kwargs):
        self.__ensure_init = True
        init(self, *args, **kwargs)

    cls.__ensure_init = False  # default value
    cls.__init__ = __init__
    cls.__new__ = staticmethod(__new__)  # staticmethod needed in py2
    return cls

foo.py

from ensure_init import ensure_init


@ensure_init
class B(object):
    def __init__(self):
        print('B.__init__')

    def f(self):
        print('B.f')


class D1(B):
    def __init__(self):
        print('D1.__init__')
        super(D1, self).__init__()

    def f(self):
        print('D1.f', type(self))


class D2(B):
    def f(self):
        print('D2.f', type(self))


class D3(B):
    def __init__(self):
        print('D3.__init__')

    def f(self):
        print('D3.f', type(self))


d1 = D1()
d1.f()
d2 = D2()
d2.f()
d3 = D3()  # TypeError: super __init__ not called