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