[Python-ideas] PEP 8 update on line length

[David Mertz]

On Tue, Feb 19, 2019, 9:07 AM simon.bordeyne <simon.bordeyne at gmail.com
wrote:

> I find that 100 to 120 characters is ideal as far as line length goes.
>

I very much hope no one else where had to read it review your code.

In my opinion, splitting lines is much worse in terms of cognitive burden
> than just a longer line. On top of that, it's not uncommon to reach 6, even
> 7 indentation levels.
>

In 20+ years of programming in Python (writing some will known books about
it too), I have never once indented a block 7 levels. Very, very rarely 6.
If you do that, your code has serious problems beyond line length.

As far as monitor size goes, I agree that on a laptop is not ideal for 100+
> characters per line if you want two pieces of code side by side.
>

In a readable size and font, I get two vertical panes of 71 characters on
my 15" Retina display. I can read a smaller font character by character,
but not easily scan a line.

Here I'm just taking about visual accuity, not the cognitive issue. My
vision in particular remains 20/20 for near vision (but sadly decayed with
age for distance). It used to be more like 20/15, but I never used lines
longer than 80 characters in any programming language (yes, individual
lines, but not as a rule). I did used to use a somewhat smaller font size
though.

I guarantee that your code quidditch would improve if you use both shorter
lines and a larger font. The latter only affects your interaction with your
screens, the former is essential to everyone who needs to look at your code.

And, fyi, I work on a 23" monitor at home and on a 15.6" monitor on the go.
> Both are perfectly fine with 100 characters a line.
>
> A good middle ground would be to enforce customization of that rule in the
> most used python linters. A simple setting to set the number of characters
> before a linting warning occurs would be acceptable.
>

Every linter I know about is customizable this way.


>
>
> Envoyé depuis mon smartphone Samsung Galaxy.
>
> -------- Message d'origine --------
> De : David Mertz <mertz at gnosis.cx>
> Date : 19/02/2019 07:28 (GMT+01:00)
> À : Anders Hovmöller <boxed at killingar.net>
> Cc : Simon <simon.bordeyne at gmail.com>, python-ideas <
> python-ideas at python.org>
> Objet : Re: [Python-ideas] PEP 8 update on line length
>
> 60, or 68, or 80 characters, is not per se a cognitive limit. Yes, sure
> whitespace counts much less towards that burden than do regular characters.
> And to a significant degrees, punctuation vs. letters vs. numbers matter.
> And sure familiar words such as keywords scan a bit easier than unfamiliar
> names of variables. And so on.
>
> But 80 characters in general is already too wide most of the time. 65 is a
> better goal as a rule of thumb, with 80 already being for exceptionally
> long lines. Python keywords are already short, there's not much improvement
> to be had there. Saving two characters for acryptic WHL isn't better than
> the word 'while', for example.
>
> Pretty much the only time my code how's more than 80 characters is when it
> includes string literally that occupy a large chunk of the width. But if
> that 50 character string is the last argument of a function call, the
> reader can mostly stop scanning at it's beginning, so it's not terrible.
> When I have many keyword arguments, I break them into multiple physical
> lines using parents too continue the logical line. Or if I have complex
> compound conditions, I give the subclauses short but descriptive names
> before the if/elif.
>
> On Tue, Feb 19, 2019, 1:11 AM Anders Hovmöller <boxed at killingar.net wrote:
>
>>
>>
>> > On 19 Feb 2019, at 05:48, David Mertz <mertz at gnosis.cx> wrote:
>> >
>> > You either have much better eyes to read tiny fonts than I do, or maybe
>> a much larger monitor (it's hard for me to fit a 30"" monitor in my laptop
>> bag).
>> >
>> > But that's not even the real issue. If the characters were in giant
>> letters on billboards, I still would never want more than 80 of them on a
>> line (well, rarely, I violate PEP 8 sometimes). Centuries if not millennia
>> of experience with writing show that cognitive burden goes up
>> exponentially, not linearly, as lines get to be more than about 60
>> characters.
>>
>> If that is the issue then we should be talking about non-space
>> characters, not a 68 column limit right? No way does 40 spaces due to
>> indent count towards the cognitive burden :)
>>
>> Also, if the cognitive burden is the issue then we should talk about
>> short forms for keyword arguments again. The way the 68 column limit works
>> in practice is that people avoid keyword arguments because of line length,
>> plus the issues already mentioned.
>>
>> / Anders
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20190219/299183ad/attachment-0001.html>