| # from http://mail.python.org/pipermail/python-dev/2001-June/015239.html | |
| # if you keep changing a dictionary while looking up a key, you can | |
| # provoke an infinite recursion in C | |
| # At the time neither Tim nor Michael could be bothered to think of a | |
| # way to fix it. | |
| class Yuck: | |
| def __init__(self): | |
| self.i = 0 | |
| def make_dangerous(self): | |
| self.i = 1 | |
| def __hash__(self): | |
| # direct to slot 4 in table of size 8; slot 12 when size 16 | |
| return 4 + 8 | |
| def __eq__(self, other): | |
| if self.i == 0: | |
| # leave dict alone | |
| pass | |
| elif self.i == 1: | |
| # fiddle to 16 slots | |
| self.__fill_dict(6) | |
| self.i = 2 | |
| else: | |
| # fiddle to 8 slots | |
| self.__fill_dict(4) | |
| self.i = 1 | |
| return 1 | |
| def __fill_dict(self, n): | |
| self.i = 0 | |
| dict.clear() | |
| for i in range(n): | |
| dict[i] = i | |
| dict[self] = "OK!" | |
| y = Yuck() | |
| dict = {y: "OK!"} | |
| z = Yuck() | |
| y.make_dangerous() | |
| print dict[z] |