[Python-ideas] Reuse "for" to express "given"

Robert Vanden Eynde robertve92 at gmail.com
Thu May 24 12:25:40 EDT 2018

It was a long time ago I couldn't easily find the post but that's alright,
you refreshed the idea :)

Let's see what others think of for x =

I also remembered some languages (like lua) use for x = range (5)
interchangeably with for x in range (5) and guido said it will never make
such a thing, for .. in being the iteration.

Le jeu. 24 mai 2018 à 18:22, Alexander Belopolsky <
alexander.belopolsky at gmail.com> a écrit :

> On Thu, May 24, 2018 at 12:04 PM Robert Vanden Eynde <robertve92 at gmail.com>
> wrote:
> > This idea was mentioned (by me) at a time yes, but wasn't written in the
> document.
> Can you point me to a specific post?  There were so may that I must have
> missed that one.
> > I think one of the thing was that it would make the grammar non LL1
> because when seeing the token "for" in a list comprehension it wouldn't
> know in advance if it's the loop or the assignment.
> I don't see how that can be a problem.  From the grammar point of view,
> "for" in "for var = <expr>" may still be seen as introducing a "loop", but
> when "=" is seen in place of "in", the compiler will resize that the "loop"
> is one a single value and emit efficient code for it.  At the AST level,
>   "for var = <expr>"  will look exactly the same as  "for var in <expr>"
> only with an "=" instead of "in".
> > And also, it might confuse people because 'for' is for iteration.
> I think I addressed this in my previous post.  Yes, for people with a
> C/C++ background, "for" may be too strongly associated with loops, but in
> mathematical sense, it seems clear that "for var in a set" means iteration
> over a set, while "for var = expression" means binding to a single value.
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