Git Pre-commit Hook For Python now with extra Python!

pre-commit.py

#!/usr/bin/env python
#-*- mode: python -*-

from subprocess import Popen, PIPE
import sys

syntax_checker = "pyflakes"

def run(command):
    p = Popen(command.split(), stdout=PIPE, stderr=PIPE)
    p.wait()
    return p.returncode, p.stdout.read().strip().split(), p.stderr.read()

_, files_modified, _= run("git diff-index --name-only --cached HEAD")

for fname in files_modified:
    if fname.endswith(".py"):
        print >>sys.stderr, "Checking syntax on %s: ... "%(fname,),
        exit_code, _, errors = run("%s %s"%(syntax_checker, fname))
        if exit_code != 0:
            print >>sys.stderr, "\rChecking syntax on %s: FAILED! \n%s"%(fname, errors)
            sys.exit(exit_code)
        else:
            print >>sys.stderr, "\rChecking syntax on %s: OK!"%(fname,)

On line 12, why do you strip and split p.stdout exactly? (I notice when reverting this, the precommit hooks fails.)

Because run is first called with a 'git diff-index' and in that case the p.stdout.read().strip().split() is a list of filenames. Of course you're right, in the pyflakes case the strip() and split() on the output is unnecessary. This would probably be easier to understand if there was a separate function for getting the list of modified file names.

Ah- Somehow I had completely missed line 14. Much easier to understand the control-flow now.

Helpful modification I've been using:

L14 should probably be

_, files_modified, _= run("git diff-index --name-only --cached HEAD")

so that non-staged files are ignored. i.e. we only run pyflakes against the files we're trying to commit, not the entire source tree.

Thanks @mtigas, I've updated the gist.