I think the proposal is reasonable and won't require a PEP. On Nov 25, 2017 3:25 PM, "Terry Reedy" <tjre...@udel.edu> wrote:
> On 11/25/2017 1:55 AM, David Cuthbert wrote: > >> First time contributing back -- if I should be filing a PEP or something >> like that for this, please let me know. >> > > I don't think a PEP is needed. > > Coming from https://bugs.python.org/issue32117, unparenthesized tuple >> unpacking is allowed in assignments: >> >> rest = (4, 5, 6) >> a = 1, 2, 3, *rest >> > > Because except for (), it is ',', not '()' that makes a tuple a tuple. > > but not in yield or return statements (these result in SyntaxErrors): >> >> return 1, 2, 3, *rest >> yield 1, 2, 3, *rest >> > > To be crystal clear, a parenthesized tuple with unpacking *is* valid. > > return (1, 2, 3, *rest) > yield (1, 2, 3, *rest) > > So is an un-parenthesized tuple without unpacking. > > Since return and yield are often the first half of a cross-namespace > assignment, requiring the () is a bit surprising. Perhaps someone else has > a good reason for the difference. Otherwise, +1 on the change. > > The unpacking in assignments was enabled by a pre-3.2 commit that I >> haven't yet been able to track back to a discussion, but I suspect this >> asymmetry is unintentional. Here's the original commit: >> https://github.com/python/cpython/commit/4905e80c3d2f6abb613 >> d212f0313d1dfe09475dc >> >> I've submitted a patch (CLA is signed and submitted, not yet processed), >> and Serihy said that since it changes the grammar I should have it reviewed >> here and have signoff by the BDFL. >> > > > > > While I haven't had a need for this myself, it was brought up by a user on >> StackOverflow (https://stackoverflow.com/questions/47272460/python-tuple- >> unpacking-in-return-statement/47326859). >> >> Thanks! >> Dave >> >> >> > > -- > Terry Jan Reedy > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/guido% > 40python.org >
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