Switching to using a universal code formatter

The title makes it sound like there may be several options, but I think black is the de facto.

So, why should we use black?

  • Consistent code base
  • Never have to worry about formatting ever again, and it looks good
  • Effectively solves about 95% of flake8 errors for you. No more annoyance trying to figure out why flake8 is yelling at you.
  • Consistent format => smaller diffs => smaller code reviews

Basically, people are allowed to write code however they want, and then before they commit, just run it through black (either manually or via a pre-commit git hook) and it will take care of any formatting for you.

As far as implementation, the recommended way is to just do one large commit that re-formats the entire codebase, and then use git-hyper-blame or git blame --ignore-rev and co to ignore that commit and still be able to see who wrote what.


Also, if you got the time here’s a cool talk from the creator of black, Lukasz Langa (who also is a core python dev)


The big question is do we accept black’s default or add some of our style changes:

–line-length = 79

I do have diffs for comparison of

black --skip-string-normalization
black --skip-string-normalization --line-length = 79
autopep8 --ignore E241,E731,W503,F405,901,FI12,FI14,FI15,FI50,FI51,FI53 PR 3673

Personally, I’m a fan of the defaults. I think the guys over at black put a lot of awesome work and thought into defining the default rules.

I would strongly prefer to keep at least --line-length=79 if we do this. I’m less familiar with the effects of --skip-string-normalization but almost certainly have less of an objection there. :smiley:

Basically, black uses " over ’ for quotes. See here, for their explanation.

--skip-string-normalization skips this check, and thus won’t auto format ’ into ".

If you are adopting Black in a large project with pre-existing string conventions (like the popular “single quotes for data, double quotes for human-readable strings”), you can pass --skip-string-normalization on the command line. This is meant as an adoption helper, avoid using this for new projects.

There’s now a PR for this.