[Python-ideas] PEP 8 update on line length

[Chris Barker]

On Thu, Feb 21, 2019 at 12:01 PM Raymond Hettinger <
raymond.hettinger at gmail.com> wrote:

> I concur.  We now put expressions in f-strings and have assignment
> expressions that easily spill over 80 characters if one uses all but the
> most compact variable names.  Comprehensions tend to make expressions
> longer.  Queries and filters in Pandas also easily spill over.  The 80
> character limit pre-dates these evolutions of the language.
>


> In particular, the case where I most want to let people run with long
> lines is in forming messages to be displayed to a user.


I agree here -- and if it's messages (also comments - a twenty char comment
after a 70 char line should be fine!) then it's not part of the logic of
the code -- so not as bd if there is some spill off the screen for those
folks that do code on tablets ;-) Actually for me, the issue s comes up
when I'm showing code on a projector -- I use a huge font so folks in the
back can see)


> class Frabawidget:
>     ...
>     @wozzle.setter
>     def (self, woozle):
>         if not (self.min_woozle < woozle < self.max_woozle):
>             raise ValueError(f"Expected woozle to be between
> {self.min_woozle} and {self.max_woozle}")
>         self._wozzle = normalize(woozle)
>

That's 103 chars long -- and very readable. But, is this that much worse?

class Frabawidget:
    ...
    @wozzle.setter
    def (self, woozle):
        if not (self.min_woozle < woozle < self.max_woozle):
            raise ValueError(f"Expected woozle to be between"
                              "{self.min_woozle} and {self.max_woozle}")
        self._wozzle = normalize(woozle)

(it IS harder to write, that's for sure)

In doing code reviews, I see many fewer atrocities from long lines than I
> do from weird line-wraps and from variable names that have been
> over-shortened to make the line fit in 80 characters.  To avoid these
> issues, my clients typically set their line limits at 90 or 100


and yet the above example was 103 ... you do need a limit somewhere.

I actually would really like the "limit" to depend on what the line is --
that is, it's OK to go longer if it's essentially text  -- message to the
user, comment, etc., rather than part of the code logic.

In fact, now that I write that, I think I actually DO do that -- and even
add a # noqa sometimes so my linter will stop bugging me. A smart linter
would be nice here.

PEP 8 is mostly about readability.  However, the line length limit often
> seems to cause less readable code.
>

So what do you suggest? simply increase the recommended line length? Or
would softening the language about extending it be enough?

Maybe something along the lines of:

A line length limit should be well defined for each project / organization
-- 80 char per line is safest for all users, but anything up to 100 is
appropriate if the team maintaining the code agrees.

Raymond: As a core dev -- are suggesting extending the line limit for the
standard library?

To all the folks quoting theory: let's be honest. Yes,  really long lines
are harder to read, but the 80 char limit comes from old terminals, NOT any
analysis that somehow that is optimum for readability.

-CHB

-- 

Christopher Barker, Ph.D.
Oceanographer

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