Reformat with YAPF

[jorisvandenbossche]

Just as an example (using the default configuration). The same files are adjusted as in #11951

[wesm]

Oof, the handling of long strings inside exceptions is pretty ugly, would benefit from manual fixes. Is there any way to get it to automatically fix them?

e.g.

raise ValueError("this is a really long message"
                 " and continued here")

[jorisvandenbossche]

Not sure, I just quickly tried it with the default settings. There are some configuration options: https://github.com/google/yapf#knobs
And I suppose you could change some of the penalties, but of course that will apply to all opening brackets, and not only to exceptions.

[jreback]

where are we on this @jorisvandenbossche is this 'enough' to make a default formatter?

[wesm]

I think we can use yapf for "fixing" code but I don't think we should use it on any automated basis. The output I see here would need quite a bit of manual fixing (cleaning up long strings in particular)

[jreback]

right. I think we are ok with the flake8 checks via Travis CI. I just want to document a 'method' of how people should go about conforming to our standard. A configurable tool is prob the best bet here (if it gets most of the way there). I was personally using autopep8 then manually fixing things. Happy to move to this tool.

[wesm]

I actually think it's good for people to fix their code manually (using flake8 on the command line) as a "learn good style the hard way" -- after a while (at least for me) you stop making style errors as you code.

[wesm]

I have this in my .emacs which show up red when I have flake8 problems

(add-hook 'python-mode-hook
      '(lambda ()
         (define-key python-mode-map "\C-m" 'newline-and-indent)
         (pylint-python-hook)
         (flymake-mode)
         (define-key python-mode-map "\M-n" 'flymake-goto-next-error)
         (define-key python-mode-map "\M-p" 'flymake-goto-prev-error)
))


;; Configure flymake for python
(when (load "flymake" t)
  (defun flymake-pylint-init ()
    (let* ((temp-file (flymake-init-create-temp-buffer-copy
                       'flymake-create-temp-inplace))
           (local-file (file-relative-name
                        temp-file
                        (file-name-directory buffer-file-name))))
      (list "flake8" (list local-file))))

  (add-to-list 'flymake-allowed-file-name-masks
               '("\\.py\\'" flymake-pylint-init)))

[jreback]

ok with that as well. maybe we need to provide more config for flake8? (its already in setup.cfg)

not sure if you can control the backslash breaking (versus parens)

[wesm]

We should put instructions in the developer docs. I looked through flake8 and I didn't see an option to check for usage of backslashes, so we may need to periodically review the codebase for cases that don't get caught during code review

[jreback]

closing in favor of #11951

[hayd]

How long did it take to run yapf on pandas? I remember it being super slow. In fact: google/yapf#96

[jreback]

that is crazy long for that file, very weird! flaking it only takes a second (500 errors though :<)

[jorisvandenbossche]

@hayd It was only a matter of seconds, but only tested on these 3 files.