I think fundamentally by special-casing a for-loop variant, you have a construct with limited/no generality that's simply an additional burden to learn. You're kind of doing the opposite of converting print from a statement into a function. I far prefer the print function because it's a function like every other and doesn't have it's own curious syntax (if only assert was also fixed..., assert(cond, reason) has bit me a few times)
It's nice that you can put *anything* that supports the iterator protocol after "for x in" and Python will "iterate" over it, however that is defined for the object. The thing might not have a useful integer index at all (dictionaries, file systems...) and the loop doesn't care. If you *do* want that index, you can enumerate() or range(len()), which I sometimes do if modifying a list in-place, but it's kinda icky as David suggests. Nick On Fri, Feb 17, 2017 at 4:31 PM, David Mertz <me...@gnosis.cx> wrote: > Iterating over range(len(collection)) is one of the worst anti-patterns in > Python. I take great pains to slap my students who do that. > > On Feb 17, 2017 9:32 AM, "Mikhail V" <mikhail...@gmail.com> wrote: > >> >> On 17 February 2017 at 17:37, Chris Angelico <ros...@gmail.com> wrote: >> >>> On Sat, Feb 18, 2017 at 3:30 AM, Mikhail V <mikhail...@gmail.com> wrote: >>> > On 17 February 2017 at 04:59, Chris Angelico <ros...@gmail.com> wrote: >>> >> >>> >> On Fri, Feb 17, 2017 at 2:13 PM, Mikhail V <mikhail...@gmail.com> >>> wrote: >>> >> > Common use case: >>> >> > >>> >> > L = [1,3,5,7] >>> >> > >>> >> > for i over len(L): >>> >> > e = L[i] >>> >> > >>> >> > or: >>> >> > >>> >> > length = len(L) >>> >> > for i over length: >>> >> > e = L[i] >>> >> >>> >> Better use case: >>> >> >>> >> for i, e in enumerate(L): >>> >> >>> > >>> > This would be more compact, yet less readable, more error prone >>> variant. >>> > I'd avoid it it all costs and even if I don't need the index further >>> in loop >>> > body, >>> > (which happens rarely in my experience) I write e=L[i] in second line >>> > to make the code more verbose and keep the flow order. >>> > So your variant (and those proposed in PEP-212) could serve in list >>> > comprehensions for example, but for common 'expanded' code I find it >>> > decline of readability, and creating totally different variants for >>> same >>> > iteration idea. >>> > But partially that could be simply matter of habit and love to >>> contractions. >>> >>> If you don't need the index, why not just iterate over the list directly? >>> >>> for e in L: >>> >>> That's the single most obvious way to step through a collection in >>> Python. What do you need to count up to the length for? >>> >>> >> I have said I need the index, probably you've misread my last comment. >> Further more I explained why I think iteration over index should be the >> preferred way, it help with readability a lot. >> All my learning years ended up with rewriting most code to "for i in >> range()" >> and I slap myself when I start to write "for e in L". >> It is exactly where TOOWTDI applies perfectly and it is integer iteration >> for me. >> >> Mikhail >> >> _______________________________________________ >> Python-ideas mailing list >> Python-ideas@python.org >> https://mail.python.org/mailman/listinfo/python-ideas >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ >
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