>>> from itertools import islice >>> a = (i for i in range(0, 100, 10)) >>> next(islice(a, 5, None))
Paul On Tue, 17 Nov 2020 at 15:37, Joao S. O. Bueno <jsbu...@python.org.br> wrote: > > Although that is not a pattern I recall I had needed, but for the first item > in a generator, > I recognize it is more complicated than it should to be able to do that. > > However, not only that would be too big a change for all this objects > I think one would expect an object providing index access with `[]` > to also have a `len`. > > Also, see it as potentially making a lot of code error-prone: > let's say one gets passed a generator where a sequence is expected. > In current Python, if an item is accessed by index, one just get an explicit > IndexError. If objects change to having indexes, two consecutive access > to `gen[1]` will consume the generator and return different values. That > could be very confusing. > > On the other hand, as I said, I can't come up with > a simple pattern to get the nth item - so probably we > should think of an easy and performant way. > > One way I can think of is to have a named parameter > to the `next` built-in that would allow one to move forward more than one > position. > > Say: `fith_element = next(gen, skip=4) ` > > and finally, one way I could think of retrieving the n > element is: > > In [19]: a = (i for i in range(0, 100, 10)) > > In [20]: next(b for i, b in enumerate(a) if i==5) > Out[20]: 50 > > It definitely feels like there should be a simpler way, > but I just could not come up with it. > > On Tue, 17 Nov 2020 at 10:35, Nuri Jung <jnoo...@snu.ac.kr> wrote: >> >> How about enabling subscription operator (`[]`) for generator expressions? >> Also for all `zip()`, `key()`, etc. They could be evaluated in the >> background only for the requested amount, to avoid evaluating the whole >> expression to something like a list or tuple, then indexed. >> _______________________________________________ >> 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/WDJWOB4NVIIQPJWBNZCF5K4SXZJIARFZ/ >> Code of Conduct: http://python.org/psf/codeofconduct/ > > _______________________________________________ > 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/BB4ZMINMSVUG4N5XOB7P25FZW2IRV67K/ > Code of Conduct: http://python.org/psf/codeofconduct/ _______________________________________________ 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/ZXF3OYEFKB42PDXGXLUXMZJ7GMPFEB7H/ Code of Conduct: http://python.org/psf/codeofconduct/
