[Python-ideas] Temporary variables in comprehensions

[Neil Girdhar]

On Fri, Feb 23, 2018 at 1:42 PM Kyle Lahnakoski <klahnakoski at mozilla.com>
wrote:

>
>
> On 2018-02-23 12:44, Neil Girdhar wrote:
>
> On Fri, Feb 23, 2018 at 12:35 PM Kyle Lahnakoski <klahnakoski at mozilla.com>
> wrote:
>
>>
>> > [
>> >     (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?
>
>>
>>
> Saving the indentation? Oh yes, for sure!  This code reads like a story,
> the indentation is superfluous to that story.  Should we add it to Python?
> I don't know; I quick scan through my own code, and I do not see much
> opportunity for list comprehensions of this complexity.
>

That's a good thing that you are not writing code like this.  I don't agree
that the indentation is "superfluous".  It makes the code easy to read.
Anyway, Google's Python style guide also agrees that very long
comprehensions like that are not worth it. (
https://google.github.io/styleguide/pyguide.html?showone=List_Comprehensions#List_Comprehensions
)

Either my data structures are not that complicated, or I have try/except
> blocks inside a loop, or I am using a real query language (like SQL).
> pythonql seems to solve all these problems well enough (
> https://github.com/pythonql/pythonql).
>

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