1 class A: 2 def __init__(self, x): 3 self.x = x 4 def __sub__(self, other): 5 return self.x - other.x 6 7 class B: 8 def __init__(self, x): 9 self.x = x 10 def __rsub__(self, other): 11 return other.x - self.x 12 13 class C: 14 def __init__(self, x): 15 self.x = x 16 17 a = A(10) 18 b = B(5) 19 c = C(3) 20 21 print a - b # 5 22 print c - b # -2 23 print a - c # 7 24 25 try: 26 print b - c # should raise an exception 27 except TypeError: 28 print "b - c: b and c do not respectively support the __sub__ and __rsub__ operations"
