Use code style Black

[matthewfeickert]

Go

Adds a pyproject.toml with Black config options, and then applies them to all the pandamonium files. Additionally, add a .pre-commit-config.yaml for a Black pre-commit hook. Additionally add the Code style Black badge to the README.

[matthewfeickert]

@dguest I'm debuging some regex with the .pre-commit-config.yaml, but I'll tag you again when this is ready for review. Feel free to give some early feedback if you have any though.

[matthewfeickert]

@dguest this is ready for review now.

[dguest]

Looks good overall. I don't have a problem with consistent formatting. There was just one place where I'm a bit surprised by black's choice (putting a space after the first index in a slice, i.e. list[x:] -> list[x :].

[dguest]

this one seems a bit weird to me: does black really insist on a space after each argument in a slice?

[matthewfeickert]

I agree that looks a bit weird, but I think this is a PEP8 adherence thing: psf/black#157

[dguest]

will black allow a space on both sides of the len(pfx)?

[matthewfeickert]

No. If you paste the following snippet

def short_fmt(fmt):
    removed_pfx = ['DAOD_']
    for pfx in removed_pfx:
        if fmt.startswith(pfx):
            return fmt[ len(pfx): ]

into the playground (https://black.now.sh/) you get back

def short_fmt(fmt):
    removed_pfx = ["DAOD_"]
    for pfx in removed_pfx:
        if fmt.startswith(pfx):
            return fmt[len(pfx) :]

[dguest]

This one is also a bit awkward, but I guess this is Black's way of telling me that I should just write a for loop.

[matthewfeickert]

Yes, to be clear, Black will not always make your code look beautiful. In many cases it will make it a bit less so. The major benefit Black gives is total offloading of mental effort of formatting, and making every commit contain only the core essence of the change (not developer style). There is a trade off here, and it might not be the right one for each project.

[dguest]

I'm fine with it. This is too long a list comprehension anyway.

[dguest]

I just realized that this is a bit weird: for better or worse (mostly worse) the target version is py27.

[matthewfeickert]

Black doesn't support or work with Python 2 at all. So target-version is a list of just the Python 3 versions it is targeting.

[matthewfeickert]

To be clear, that doesn't mean that Python 2 support of the code needs to be dropped. Just that to actually run Black you need a Python 3 runtime.

[dguest]

Interesting, I guess as long as black doesn't have a tendency to make changes that are more than aesthetic in python 2 this is fine.

[matthewfeickert]

Black does introduce trailing commas in some tuples or lists, which will be viewed as invalid syntax in Python 2. However, this is not the case for pandamonium, and so it is unaffected.

FWIW, I have never had this break code for me.

[dguest]

I don't even think that's a syntax error in python 2:

> python2 -c 'l=[1,2,3,]; t=(3,4,5,); print(l,t)'
([1, 2, 3], (3, 4, 5))

[matthewfeickert]

Huh. Yeah, I guess I'm wrong on where this causes problems. I have seen examples of Black breaking working Python 2 code, but apparently I don't remember how and this is hard to do.

[matthewfeickert]

@dguest Ping on this given a recent update to Black.

[matthewfeickert]

Thanks @dguest

[dguest]

All you can handle bro!