#!/usr/bin/env python

class A:
    x = []

    def add(self):
        self.x.append(1)


class B:
    def __init__(self):
        self.x = []

    def add(self):
        self.x.append(1)


x = A()
y = A()
x.add()
y.add()
print "A's x:",x.x

x = B()
y = B()
x.add()
y.add()
print "B's x:",x.x