1 class C: 2 def f(self): 3 return self.x 4 5 class D(C): 6 pass 7 8 class E(C): 9 def __init__(self, x): 10 self.x = x 11 12 d = D() 13 print d.f() 14 15 e = E(2) 16 print e.f()