[issue34751] Hash collisions for tuples

[Jeroen Demeyer]

Jeroen Demeyer <J.Demeyer at UGent.be> added the comment:

While writing up the analysis above, it occurred to me that collisions already happen for 2-tuples:

>>> hash((3, -2)) == hash((-3, 0))
True

These kind of 2-tuples of small integers don't look contrived at all. I can easily see them appearing, in mathematical applications for example.

As for real-world usage: the only thing that I can say is that I discovered these hash collisions a while ago, while working on SageMath. I was testing the hash for a custom class and I found collisions, which I traced back to collisions for tuples.

In any case, it is hard to find real-world problems where a bad hash really matters, since Python works fine with a broken hash too.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34751>
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