class Foo:
    attr = 1
    def __repr__(self):
        return "%s()" % self.__class__.__name__

class Bar(Foo):
    __attr = 1
    def __init__(self, ha=12):
        self.attr = 12

class Baz(Bar):
    def test(self, arg):
        self.attr = arg

a = Foo()
b = Bar()
c = Baz()
c.test(b)
if c.attr == a.attr:
    print a
elif c.attr == b:
    print b
print c