Silly example of defining a class inside another class

ugmo.py

class A(object):

    def __init__(self, f, mood):
        self.f = f
        self.mood = mood

    def make_class(self):

        class C(object):

            # self here refers to the instance of A, not an instance of
            # C!
            my_method = self.f

            if self.mood == 'happy':

                # But this "self" refers to the instance of C...
                def walk(self):
                    print("With a spring in my step")

            else:

                def walk(self):
                    print("So glum")


        return C

if __name__ == "__main__":

    a = A(lambda self, x: x+x, 'happy')
    bigC = a.make_class()

    c = bigC()
    print("c.my_method(4) returned {0}.".format(c.my_method(4)))

    c.walk()