Format code with Black

[hugovk]

I'd like to suggest formatting the code with Black:

By using Black, you agree to cede control over minutiae of hand-formatting. In return, Black gives you speed, determinism, and freedom from pycodestyle nagging about formatting. You will save time and mental energy for more important matters.

Black makes code review faster by producing the smallest diffs possible. Blackened code looks the same regardless of the project you’re reading. Formatting becomes transparent after a while and you can focus on the content instead.

https://black.readthedocs.io/en/stable/the_black_code_style.html

Black intentionally doesn't provides many options, and I've not used them here. The idea is you just run black and it takes care of everything for you.

I added #fmt:off/fmt:on to retain formatting only where the shape of a list is important, for matrices.

Only the src directory has been done here for demonstration, let me know what you think.

[jdufresne]

I like it 👍

I've seen more and more Python projects adopt black such that it now seems very natural style to me. I think it makes the process easier for new contributors as they won't need to stress or think about the project's coding style. Instead just let the tool handle it.

As a mere infrequent outside contributor, I'm for it.

[radarhere]

Provided it is just run automatically over new code, I could see this as being a time saver. On the other hand, will new contributors be confused about why their code has rearranged itself?

Note that you'd also want to add this to requirements.txt

[hugovk]

Provided it is just run automatically over new code, I could see this as being a time saver. On the other hand, will new contributors be confused about why their code has rearranged itself?

You do need to run the command, it's not in a pre-commit hook or anything (but if they wished they could create one, or add it to their editor on save). But it's just a pip install black && black <dir>. It will fix lots of potential flake8 errors too.

On the CI, black --check --diff will show any fixes it would have made in case someone wants to make the changes manually and without the tool.

Note that you'd also want to add this to requirements.txt

Added.

[hugovk]

If no other comments, let's merge this and I'll make a new PR for the other directories.

[radarhere]

Consider merging in #3898 first, before the changes from this PR make a simple revert unviable.

[hugovk]

Yep, good idea.