On Mon, Nov 27, 2017 at 11:31 PM, Kirill Balunov <kirillbalunov@gmail.com> wrote:
In terms of language proposals, you can't just say "don't need values for"; the semantics have to be EITHER "consume and discard" OR "don't consume". We already have a perfectly good way of spelling "consume and discard":
x, y, _ = iter
You mean ( x, y, *_ = iter ) ?
Uhh, yeah, that's what I meant. Sorry. Anyhow, point is, there IS a syntax for that, so we don't need another.
The proposed semantics, if I understand you correctly, are:
try: _iter = iter(it) x = next(_iter) y = next(_iter) except StopIteration: raise ValueError # no "else" clause, we're done here
Yes, "roughly" this semantics is proposed, with some assumptions on _iter = iter(it). As I can see at the moment, these cases should behave differently:
x, y = [1,2,3,4] # must raise ValueError x, y = iter([1,2,3,4]) # should work
But at the same time, it violates current situation. So maybe, as you have said we need special syntax. I will think about it.
That's the part I disagree with, but if you're the PEP author, you can make the recommendation be anything you like. However, one very strong piece of advice: it's easier to get a proposal accepted if the backward compatibility section simply says "the proposed notation is a SyntaxError in current versions of Python". Changing the semantics of currently legal code requires that you demonstrate that the current semantics are, in some way, faulty or buggy. ChrisA