Very practical question

[madpython]

I've been doing an application with Tkinter widgets. Nothing really
fancy just routine stuff. Though I have no problems with it by now I
guess it would be reasonable to ask about a thing that's been bothering
me a bit. Look at this piece of code:

class A(object):
    def a(self):
        return "a from A"

class B(object):
    def interClassCall(self):
        print globals()['c'].__dict__['a'].a()

class C(object):
    def __init__(self):
        self.a=A()
        self.b=B()
    def c(self):
        self.b.interClassCall()

if __name__=="__main__":
    c=C()
    c.c()

What is another way to get data from method of another instance of a
class? Or maybe print globals()['c'].__dict__['a'].a() is perfectly
normal. I need your professional expertise.