Message326214
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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Date |
User |
Action |
Args |
2018-09-24 09:52:53 | jdemeyer | set | recipients:
+ jdemeyer, tim.peters, rhettinger, mark.dickinson, eric.smith, sir-sigurd |
2018-09-24 09:52:53 | jdemeyer | set | messageid: <1537782773.24.0.956365154283.issue34751@psf.upfronthosting.co.za> |
2018-09-24 09:52:53 | jdemeyer | link | issue34751 messages |
2018-09-24 09:52:53 | jdemeyer | create | |
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