Michael Seifert added the comment: > I explored that notion of iterator length transparency years ago. While I > don't remember all the details, I did record some notes at the top of > Lib/test/test_iterlen.py.
But isn't that the point of the length_hint? To provide an *estimate* for the length? So generally I would expect the length_hint to be accurate (at least accurate enough to avoid reallocations) for well-behaved iterators. And I think that's possible for "zip" and "map" (but also for several itertools: product, permutations, combinations, islice, accumulate, starmap, zip_longest). At least in theory. Also it would allow to prohibit infinite iterators to be passed to "length_hint"-aware functions. For example `list(count())` could raise an exception when `count.length_hint` would return math.inf or sys.maxsize + 1. The pull request was just because I was curious how it performed and wanted to share the code. Feel free to reject it. The performance improvement wasn't amazing in the micro-benchmarks. ---------- nosy: +MSeifert _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue26828> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
