1 # from http://mail.python.org/pipermail/python-dev/2001-June/015239.html 2 3 # if you keep changing a dictionary while looking up a key, you can 4 # provoke an infinite recursion in C 5 6 # At the time neither Tim nor Michael could be bothered to think of a 7 # way to fix it. 8 9 class Yuck: 10 def __init__(self): 11 self.i = 0 12 13 def make_dangerous(self): 14 self.i = 1 15 16 def __hash__(self): 17 # direct to slot 4 in table of size 8; slot 12 when size 16 18 return 4 + 8 19 20 def __eq__(self, other): 21 if self.i == 0: 22 # leave dict alone 23 pass 24 elif self.i == 1: 25 # fiddle to 16 slots 26 self.__fill_dict(6) 27 self.i = 2 28 else: 29 # fiddle to 8 slots 30 self.__fill_dict(4) 31 self.i = 1 32 33 return 1 34 35 def __fill_dict(self, n): 36 self.i = 0 37 dict.clear() 38 for i in range(n): 39 dict[i] = i 40 dict[self] = "OK!" 41 42 y = Yuck() 43 dict = {y: "OK!"} 44 45 z = Yuck() 46 y.make_dangerous() 47 print dict[z] 48
