Author jdemeyer
Recipients eric.smith, jdemeyer, mark.dickinson, rhettinger, sir-sigurd, tim.peters
Date 2018-09-24.09:52:53
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Message-id <1537782773.24.0.956365154283.issue34751@psf.upfronthosting.co.za>
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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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2018-09-24 09:52:53jdemeyersetrecipients: + jdemeyer, tim.peters, rhettinger, mark.dickinson, eric.smith, sir-sigurd
2018-09-24 09:52:53jdemeyersetmessageid: <1537782773.24.0.956365154283.issue34751@psf.upfronthosting.co.za>
2018-09-24 09:52:53jdemeyerlinkissue34751 messages
2018-09-24 09:52:53jdemeyercreate