To stir up some more fire, I would personally be fine with sets having the same ordering guarantees as dicts, *IF* it can be done without performance degradations. So far nobody has come up with a way to ensure that. "Sets weren't meant to be deterministic" sounds like a remnant of the old philosophy, where we said the same about dicts -- until they became deterministic without slowing down, and then everybody loved it. Regarding hash(None), I think that there is something to be said for making that stable, and the arguments against it feel like rationalizations for FUD. We've survived way larger controversies. I also note that hash(()) is apparently stable. On Mon, Nov 28, 2022 at 3:16 PM Oscar Benjamin <oscar.j.benjamin@gmail.com> wrote:
On Mon, 28 Nov 2022 at 22:56, Brett Cannon <brett@python.org> wrote:
On Sun, Nov 27, 2022 at 11:36 AM Yoni Lavi <yoni.lavi.p@gmail.com>
wrote:
All it takes is for your program to compute a set somewhere with
affected keys, and iterate on it - and determinism is lost.
That's actually by design. Sets are not meant to be deterministic conceptually as they are essentially a bag of stuff. If you want deterministic ordering you should convert it to a list and sort the list.
What does "sets are not meant to be deterministic" even mean?
Mathematically speaking sets are not meant to be ordered in any particular way but a computational implementation has to have some order and there is no reason to prefer non-deterministic order in general. Actually determinism in a computational context is usually a very valuable feature. I find it hard to see why non-determinism is "by design".
Also it isn't usually possible to sort a list containing None:
In [9]: sorted([None, 1, 2]) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-9-344383189210> in <module> ----> 1 sorted([None, 1, 2])
TypeError: '<' not supported between instances of 'int' and 'NoneType'
It would be useful to have a straight-forward way to sort a set into a deterministic ordering but no such feature exists after the Py3K changes (sorted used to do this in Python 2.x).
-- Oscar _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/ILP2ZKVX... Code of Conduct: http://python.org/psf/codeofconduct/
-- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-c...>