копирование объектов

#!/usr/bin/env python
#coding:utf-8

import copy

class B(object):
    b = 0

class A(object):

    b = 0
    
    def __init__(self):
        self.a = B()
        
a = A()
b = a
c = copy.copy(a)
d = copy.deepcopy(a)
a.a.b = 1
a.b = 1
print b.a.b, b.b
print c.a.b, c.b
print d.a.b, d.b