On Mon, Jul 13, 2020 at 7:44 AM Guido van Rossum <gu...@python.org> wrote:
> I think you all should get together and come up with a good > implementation, > +1 > and then petition Raymond Hettinger. Is this Raymond's turf? I would think it belongs more in the random module than itertools, or is that Raymond's responsibility as well? In any case, a good implementation would be a lot easier to evaluate for inclusion. Or maybe there is an existing open source 3rd party project that has code > you can copy? I don’t recall if random has a C accelerator, but if it does, > you should come up with C code as well. > Or Cython— at least to prototype it. -CHB > —Guido > > On Mon, Jul 13, 2020 at 05:40 David Mertz <me...@gnosis.cx> wrote: > >> If we get this function (which I would like), the version with k items >> (default 1) is much better. Some iterators cannot be repeated at all, so >> not only is it slower to call multiple times if you need k>1, it's >> impossible. >> >> On Mon, Jul 13, 2020, 8:37 AM David Mertz <me...@gnosis.cx> wrote: >> >>> This is an inefficient reservoir sampling. The optimized version does >>> not need to call a random inclusion switch on every element, but can skip a >>> geometrically ordered collection of (random) skip lengths to avoid most >>> random inclusion decisions. >>> >>> Obviously, all items must be iterated over no matter what, but if >>> randrange() is significant compared to the cost of next(), the >>> skip-then-decide version is much preferred, especially as size grows. >>> >>> On Mon, Jul 13, 2020, 7:53 AM Oscar Benjamin <oscar.j.benja...@gmail.com> >>> wrote: >>> >>>> I posted this in the thread about indexing dict items but it seems to >>>> have been buried there so I'm starting a new thread. >>>> >>>> Maybe there could be a function in the random module for making a >>>> random choice from an arbitrary (finite) iterable. This implementation >>>> can choose a random element from an iterable by fully iterating over >>>> it so is O(N) in terms of CPU operations but O(1) for memory usage: >>> >>> [,,,] > >> >>>> -- > --Guido (mobile) > _______________________________________________ > 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/DZ7KQZM5EQO4YIN3A3RW6BAKOP2CXWP3/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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