Run autopep8 and any tests you can find. To have a as a pre-commit hook, add to .git/hooks/pre-commit

pre-commit.sh

#!/usr/bin/env bash

# Script to run before doing a commit. This will run autopep8 and any unit tests it can find.
# Place this script in .git/hooks/ directory of your repo and rename it pre-commit (no extension)
# To have this file copied to every new repo you created, place it in $HOME/.git_template/hooks/pre-commit

# NOTES:
# 1. This is an opinionated script, following the notion that code formatting issues are the most contentious but the
#    least consequential. As such it borrows a page from Go and lets the machine decide on the formatting. Concretely,
#    this means that any PEP8 violations will be fixed before commit, so long as the semantics of the code aren't changed
#    (e.g. x == None is not replaced with x is None)
#
# 2. If any tests fail the commit will be aborted. To force a commit (at your own peril!), use 'git commit --no-verify'


function python_checks {
    staged=$1
    # test that we have autopep8.
    which autopep8 > /dev/null 2>&1
    # examine exit status
    if [ $? -gt 0 ]; then
        echo "autopep8 not installed. Cannot proceed"
        exit 1
    fi

    # run autopep8 to see if changes need to made.
    mln=120 # max line length. Should be something sensible for the modern world.
    autopep_results=$(autopep8 --max-line-length ${mln} --diff ${staged})


    if [ "$autopep_results" != "" ]; then
        # if colordiff is installed, we'll use it.
        which colordiff > /dev/null 2>&1
        if [ $? -eq 0 ]; then
            echo "$autopep_results" | colordiff
        else
            echo "$autopep_results"
        fi


        # Make the changes.
        autopep8 --max-line-length ${mln} --in-place ${staged}
        # And restage.
        git add ${staged}
    fi


    # run tests
    python -m unittest discover . --failfast
    # unittest exists with 0 if all tests passed, 1 otherwise.
    tests_failed=$?
    if [ ${tests_failed} -eq 1 ]; then
        echo "Tests failed. Aborting commit"
        exit 1
    fi
}

# Look for python files that are about to be committed.
staged_py_files=$(git diff --name-only --cached | grep "\.py$")
if [[ ! -z "$staged_py_files" ]]; then
    python_checks ${staged_py_files}
fi

exit 0