Somewhere in the sources of Zope I've seen a technique similar to this, to get to the locals of the caller object. Although interesting to know, actually deploying this technique makes the code hard to understand, so I would advice against it. Still, I'm recording it here, for my own reference.

import sys

def do():
    frame = sys._getframe(1)
    caller = frame.f_locals['self']
    print caller.secret

class A(object):
    secret = "Hello world"
    def __init__(self):
        do()

if __name__ == "__main__":
    A()