1 class C: 2 def __init__(self): 3 self.x = 1 4 def f(self): 5 return self.x 6 7 class D(C): 8 pass 9 10 class E(C): 11 def __init__(self, x): 12 self.x = x 13 14 d = D() 15 print d.f() 16 17 e = E(2) 18 print e.f()