On Sat, Mar 3, 2018 at 7:31 AM, Brendan Barnwell <brenb...@brenbarn.net> wrote: > On 2018-03-02 12:20, Chris Angelico wrote: >> >> On Sat, Mar 3, 2018 at 7:04 AM, Eric Fahlgren <ericfahlg...@gmail.com> >> wrote: >>> >>> >>> On Fri, Mar 2, 2018 at 10:27 AM, Jelle Zijlstra >>> <jelle.zijls...@gmail.com> >>> wrote: >>>> >>>> >>>> >>>> I wonder if we could have a more limited change to the language that >>>> would >>>> allow only the as/while use cases. Specifically, that means we could do: >>>> >>>> while do_something() as x: >>>> print(x) >>> >>> >>> >>> The "while" case is the only part of the PEP that has any traction with >>> me. >>> It doesn't add any keywords, scope can be identical to "with" and it >>> cleans >>> up a code pattern that is very common. >> >> >> How often do you have a loop like this where you actually want to >> capture the exact condition? I can think of two: regular expressions >> (match object or None), and socket read (returns empty string on EOF). >> This simplified form is ONLY of value in that sort of situation; as >> soon as you want to add a condition around it, this stops working (you >> can't say "while do_something() is not _sentinel as x:" because all >> you'll get is True). And if you are looking for one specific return >> value as your termination signal, you can write "for x in >> iter(do_something, None):". > > > But you could have "while (do_something() as x) is not _sentinel". > Not sure how proponents and opponents would react to that. Limiting the > SLNB to the beginning of block-level statements seems perverse in a way, but > also might cut down on gratuitous overuse mixed into all kinds of weird > positions in statements. >
If we're going to have something that's syntactically valid in an expression, I don't see a lot of value in requiring that it be inside a while or if header. That just leads to confusion and mess down the road. ChrisA _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
