import inspect

class A:
    def caller(self):
        frames = inspect.getouterframes(inspect.currentframe())
        return inspect.getargvalues(frames[2][0]).locals.get("self")

    def bar(self):
        print self.caller()


class B:
    def bar(self):
        A().bar()

B().bar()

##################################
<__main__.B instance at 0x004C3AA8>