On 2020-07-28 at 15:58:58 -0700, Christopher Barker <python...@gmail.com> wrote:
> But a dict always has a LOT fewer buckets than possible hash values, > so clashes within a bucket are not so rare, so equality needs to be > checked always -- which is what I was missing. > And while it wouldn't break anything, having a bunch of non-equal > objects produce the same hash wouldn't break anything, it would break > the O(1) performance of dicts. > Have I got that right? Yes. Breaking O(1) performance was actually the root of possible Denial of Service attacks: if an attacker knows the algorithms, that attacker could specifically create keys (e.g., user names) whose hash values are the same, and then searching a dict degenerates to O(N), and then your server falls to its knees. At some point, Python added some randomization to the way dictionaries work in order to foil suck attacks. _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/TJCGVDGZWP4LXG44P4Z34BPMZRI3ODY3/ Code of Conduct: http://python.org/psf/codeofconduct/
