I'm not a huge fan. Sure, dicts are ordered now, but I doubt that many people use that feature. I honestly still think of them as unordered ;)
Let's talk code clarity. After all, to quote GvR, "Code is more often read than written." (I may have gotten the wording wrong, I just wrote it off the top of my head.) To me, the presence of a dict suggests that order doesn't matter. If you want order, communicate that by using `collections.OrderedDict`, a fully-featured dict subclass where the point is the order! You can get the first or last key/item pairs with `.popitem()`. It works! OrderedDict documentation: https://docs.python.org/3.10/library/collections.html#collections.OrderedDict We could add indexing to OrderedDict, which would return key/value pairs. (While we're talking about collections, why don't we return a namedtuple ;) ) As for adding functions to `itertools`, sure, I'm for it. We don't need people writing `next(iter(iterable))` just to get the first item. -- Finn On Wed, Oct 6, 2021, 8:02 AM Steven D'Aprano <st...@pearwood.info> wrote: > On Wed, Oct 06, 2021 at 11:11:09AM +0100, Alex Waygood wrote: > > > The temptation to insist "see, YAGNI!" at this point I shall resist. > > > > *You* might not need it, but I've seen it come up a lot on Stack > > Overflow, and all too often people end up going for the much less > > efficient solution. I personally have also written code with practical > > applications using `next(iter(mydict))`. > > Under what circumstances do you care what the first key in a dict is, > without going on to care about the second, third, fourth etc? > > They are surely extremely niche, or artificial, or both, e.g. the > Stackoverflow problem you link to: "find the first non-repeating > character in a string -- using only one loop". Why the *first* rather > than any, or all? > > In any case, the presence of one or two uses for a piece of > functionality doesn't mandate that we make this a builtin. Your solution > with next() is perfectly adequate. > > The other suggested methods are even more obscure. Why have a method > for returning the first value, without knowing the key? > > "I don't know what the first key is, and I don't care, but I know that > whatever it is, it maps to the value 17." > > Now what are you going to do with that knowledge? This seems like a > method in desperate need of a use-case. > > > [...] > > I agree that it's a lot of methods to add. That's precisely why I > > prefer Inada Naoki's suggestion of additions to itertools > > Whether they are added to dict or itertools, there are still nine of > them, and they are pretty much near clones of each other: > > # first_ and last_ whatsits > next([iter|reversed](obj.[keys|values|items]())) > > if you will excuse the misuse of hybrid Python/BNF syntax :-) > > > > -- > Steve > _______________________________________________ > 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/T3TOFAFBPGY44LOVKSMVZJGBNQ7MUNEL/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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