On Sun, May 08, 2022 at 11:02:22AM +1000, Chris Angelico wrote:
> On Sun, 8 May 2022 at 10:23, Steven D'Aprano <st...@pearwood.info> wrote:
> > Outside of that narrow example of auto-assignment of attributes, can
> > anyone think of a use-case for this?
> >
>
> Honestly, I don't know of any. But in response to the objection that
> it makes no sense, I offer the perfectly reasonable suggestion that it
> could behave identically to other multiple assignment in Python.
Nobody says that it makes "no sense". Stephen Turnbull suggested it
doesn't make "much sense", but in context I think it is clear that he
meant there are no good uses for generalising this dotted parameter
name idea, not that we can't invent a meaning for the syntax.
> There's not a lot of places where people use "for x, x.y in iterable",
> but it's perfectly legal. Do we need a use-case for that one to
> justify having it, or is it justified by the simple logic that
> assignment targets are populated from left to right?
The analogy breaks down because we aren't talking about assignment
targets, but function parameters. Function parameters are only
*kinda sorta* like assignment targets, and the process of binding
function arguments passed by the caller to those parameters is not as
simple as
self, x, x.y = args
The interpreter also does a second pass using keyword arguments, and a
third pass assigning defaults if needed. Or something like that -- I
don't think the precise implementation matters.
Of course we could make it work by giving *some* set of defined
semantics, but unless it is actually useful, why should we bother? Hence
my comment YAGNI.
> I'm not advocating for this, but it shouldn't be pooh-poohed just
> because it has more power than you personally can think of uses for.
Power to do *what*?
If nobody can think of any uses for this (beyond the auto-assignment of
attributes), then what power does it really have?
I don't think "power" of a programming language feature has a purely
objective, precise definition. But if it did, it would surely have
something to do with the ability to solve actual problems.
--
Steve
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