Python singleton with closure scopes

# It will be slightly harder to create multiple instances of this class

class S:
    def __init__(self, arg1, arg2):
        # Dummy method. Used for reflection only
        pass

    @classmethod
    def get_instance(cls, arg1, arg2):
        # Dummy method. Used for reflection only
        pass

    @staticmethod
    def initialize():
        magic_value = object()
        instances = [None]

        def __init__(self, arg1, arg2, secret_arg=None):
            if secret_arg is not magic_value:
                raise Exception("Told you this is a singleton")

            self.arg1 = arg1
            self.arg2 = arg2

        @classmethod
        def get_instance(cls, arg1, arg2):
            print("That's the way to do it!")
            if instances[0]:
                instances[0] = cls(arg1, arg2, magic_value)

            return instances[0]

        return {'__init__': __init__, 'get_instance': get_instance}

    locals().update(initialize.__func__())
    del initialize


if __name__ == '__main__':
    s1 = S.get_instance(1,2)

    s2 = S.get_instance(3,4)
    print(s2 is s1)
    
    S(2,2)