[Python-ideas] Temporary variables in comprehensions

[Neil Girdhar]

On Fri, Feb 23, 2018 at 12:35 PM Kyle Lahnakoski <klahnakoski at mozilla.com>
wrote:

> I believe list comprehensions are difficult to read because they are not
> formatted properly. For me, list comprehension clauses are an
> expression, followed by clauses executed in the order. Any list
> comprehension with more than one clause should be one-line-per clause.
>
> Examples inline:
>
> On 2018-02-15 19:57, Steven D'Aprano wrote:
> > Where should the assignment go? [(y, y**2) let y = x+1 for x in (1, 2,
> > 3, 4)] [(y, y**2) for x in (1, 2, 3, 4) let y = x+1]
>
> Since y is a function of x, it must follow the for clause:
>
> > [
> >     (y, y ** 2)
> >     for x in (1, 2, 3, 4)
> >     let y = x + 1
> > ]
>
> > How do they interact when you have multiple loops and if-clauses? [(w,
> > w**2) for x in (1, 2, 3, 4) let y = x+1 for a in range(y) let z = a+1
> > if z > 2 for b in range(z) let w = z+1]
>
> They are applied in order:
>
> > [
> >     (w, w**2)
> >     for x in (1, 2, 3, 4)
> >     let y = x+1
> >     for a in range(y)
> >     let z = a+1
> >     if z > 2
> >     for b in range(z)
> >     let w = z+1
> > ]
>
> which is a short form for:
>
> > def stuff():
> >     for x in (1, 2, 3, 4):
> >         y = x+1
> >         for a in range(y):
> >             z = a+1
> >             if z > 2:
> >                 for b in range(z):
> >                     w = z+1
> >                     yield (w, w**2)
> >
> > list(stuff())
>

Is it that much shorter that it's worth giving up the benefit of
indentation?

>
>
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