util.py

#!/usr/bin/env python
# From https://github.com/pre-commit/pre-commit-hooks
# License: MIT

from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals

import subprocess
import os

devnull = open(os.devnull, 'w')


class CalledProcessError(RuntimeError):
    pass


def added_files():
    out, err, rc = cmd_output('git', 'diff', '--staged', '--name-only')
    return set([f for f in out.splitlines() if f.endswith('py')])


def cmd_output(*cmd, **kwargs):
    retcode = kwargs.pop('retcode', 0)
    popen_kwargs = {'stdout': subprocess.PIPE, 'stderr': subprocess.PIPE}
    popen_kwargs.update(kwargs)
    proc = subprocess.Popen(cmd, **popen_kwargs)
    stdout, stderr = proc.communicate()
    stdout = stdout.decode('UTF-8')
    if stderr is not None:
        stderr = stderr.decode('UTF-8')
    if retcode is not None and proc.returncode != retcode:
        raise CalledProcessError(cmd, retcode, proc.returncode, stdout, stderr)
    return stdout, stderr, proc.returncode


def execute(cmd, silent=False):
    if silent:
        params = {
                'stdout': devnull,
                'stderr': devnull,
                }
    else:
        params = {}
    retcode = subprocess.call(cmd.split(), **params)
    return retcode


def exists(cmd):
    return execute('which %s' % cmd, silent=True) == 0