New assignmens ...

[Chris Angelico]

On Wed, Oct 27, 2021 at 6:00 PM Antoon Pardon <antoon.pardon at vub.be> wrote:
>
>
>
> Op 26/10/2021 om 00:24 schreef Chris Angelico:
> > TBH, I don't think there's a lot of value in multiple-assignment,
> > since it has a number of annoying conflicts of syntax and few viable
> > use-cases. But if you have great examples of "x.y :=" or "x[y] :=",
> > then by all means, post on python-ideas to propose widening the scope.
>
> I think you should seperate the costs from the benefits. It is not because
> the costs can be high there is little value.
>
> And how do you count use cases? What about the following pattern:
>
> while (a, b) := next_couple(a,b)[-1]:
>      ...
>
> Is that one use case or is that a use case for each kind of couple?
>
> And even if the benefits are little per case, they can add up with every
> occasion such a case pops up.
>

I'm not sure that it's much of a use-case; isn't it an infinite loop as written?

And that's the problem. With multiple-assignment, the overall value is
going to be the tuple, so you then have to add extra parentheses and
subscripting to get what you want to check. That makes it far less
clean, far less tempting, far less valuable. You have to parenthesize
the assignment target (otherwise it'll build a tuple out of one value
and the assigned target), then parenthesize again, and subscript at
the end.

So if you want this added, show a use-case that makes it look way
better than the alternatives (including a generator, a mid-loop break,
etc).

ChrisA