On Mon, 20 Jun 2022 at 21:11, Jonathan Fine <jfine2...@gmail.com> wrote: > > Hi > > Some have liked adding a new syntax > a, b, ... = iterable > to mean consume two items from the iterable. However, > a, b, Ellipsis = iterable > has a different meaning (at least in Python 3.8). It redefines Ellipsis. (As > an explicit constant, '...' can be redefined.)
To clarify: The syntactic token '...' will always refer to the special object Ellipsis (at least back as far as Python 3.4 - can't remember when it became available in all contexts), but the name Ellipsis can be rebound. So even though, in many contexts, "x = Ellipsis" and "x = ..." will have the same net effect, they are distinct (one is a name lookup and the other is a constant), and they're definitely different in assignment. (Though it wouldn't surprise me if a future Python release adds Ellipsis to the set of non-assignable names, with None/True/False.) > The syntax > a, b, ... = iterable > so to speak fills a gap in existing syntax, as the construct is at present > invalid. I actually like gaps in syntax, for the same reason that I like a > central reservation in a highway. The same goes for the hard shoulder / > breakdown lane. > > The title of this thread includes the phrase 'Stop Iterating' (capitals > added). This suggests the syntax > a, b, StopIterating = iterable > where StopIterating is a new keyword that can be used only in this context. > > I'd like to know what others think about this suggestion. > Hard no. That is currently-legal syntax, and it's also clunky. I'd much rather the "assign to ..." notation than a weird new soft keyword that people are going to think is a typo for StopIteration. It's worth noting that the proposed syntax has a slight distinction from the normal asterisk notation, in that it makes perfect sense to write this: a, *_, b = thing but does not make sense to write this: a, ..., b = thing as the "don't iterate over this thing" concept doesn't work here. (Supporting this would require some way to reverse the iterator, and that's not a language guarantee.) ChrisA _______________________________________________ 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/SYZK4GBLMCKWQK4Z5OEJWGYORBWPBU6K/ Code of Conduct: http://python.org/psf/codeofconduct/
