Auto post-commit PEP8 correction

It’s always an hateful job to correct PEP8 warnings manually.

$ flake8 billy --ignore=E501,W293
billy/tests/integration/test_basic.py:401:45: W291 trailing whitespace
billy/models/processors/balanced_payments.py:116:44: W291 trailing whitespace
billy/models/processors/balanced_payments.py:133:30: W291 trailing whitespace

I bet you don’t like this either. Today I cannot take it anymore. I was wondering, why I should do this thing machine should do? So I seek solutions on the Internet, and I found an article looks helpful - Syntax+pep8 checking before committing in git. The basic idea is to add a pre-commit hook script to git for checking PEP8 syntax before commit. By doing that, you cannot commit code with PEP8 warnings anymore, when you do, you see errors like this

$ git commit
billy/tests/integration/test_basic.py:401:45: W291 trailing whitespace
billy/models/processors/balanced_payments.py:116:44: W291 trailing whitespace
billy/models/processors/balanced_payments.py:133:30: W291 trailing whitespace

Which is great, but still, you need to correct these syntax issues manually. I thought there must be something can do these boring job for you. And yes, I found autopep8. I can use autopep8 in pre-commit hook to correct PEP8 issues for me. However, I don’t think it is a good idea to let code formatting tool modifies your code silently when committing. I want to know what is modified by the tool. So here comes another solution, I use post-commit hook instead to compare the latest commit with previous commit:

#!/bin/sh
FILES=$(git diff HEAD^ HEAD --name-only --diff-filter=ACM | grep -e '\.py$')

for f in $FILES
do
    # auto pep8 correction
    autopep8 --in-place --ignore=E309,E501,W293 $f
done

All you need to do is install autopep8

pip install autopep8

and put the post-commit script at .git/hooks/post-commit. In this way, once I do a commit, it will correct PEP8 issues for me. I can review what is modified there, and make another PEP8 correction commit. With this, you can eventually enjoy coding rather than wasting time in removing trailing whitespace everywhere :D