[Python-ideas] How assignment should work with generators?

[Guido van Rossum]

On Mon, Nov 27, 2017 at 1:32 PM, Chris Angelico <rosuav at gmail.com> wrote:

> On Tue, Nov 28, 2017 at 8:24 AM, Guido van Rossum <guido at python.org>
> wrote:
> > On Mon, Nov 27, 2017 at 1:18 PM, Greg Ewing <greg.ewing at canterbury.ac.nz
> >
> > wrote:
> >>
> >> Chris Angelico wrote:
> >>>
> >>> The problem is that it depends on internal whitespace to
> >>> distinguish it from augmented assignment;
> >>
> >>
> >> Ah, didn't spot that. I guess the ellipsis is the next best
> >> thing then.
> >>
> >> An alternative would be to require parens:
> >>
> >>    (x, y, *) = z
> >
> >
> > But that would have the same issue.
> >
> > Is this problem really important enough that it requires dedicated
> syntax?
> > Isn't the itertools-based solution good enough? (Or failing that,
> couldn't
> > we add something to itertools to make it more readable rather than going
> > straight to new syntax?)
>
> I don't think there's much that can be done without syntax; the
> biggest problem IMO is that you need to tell islice how many targets
> it'll be assigned into. It needs some interpreter support to express
> "grab as many as you have targets for, leaving everything else behind"
> without stating how many that actually is. So the question is whether
> that is sufficiently useful to justify extending the syntax. There are
> a number of potential advantages and several competing syntax options,
> and this suggestion keeps coming up, so I think a PEP is warranted.
>

OK, that's reasonable, and at first blush the ellipsis proposal looks okay.
My PEP queue for Python 3.7 is full though, so I would like to put this off
until 3.8.

-- 
--Guido van Rossum (python.org/~guido)
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