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