I think that this may be unnecessary given the existence of the sh[1] Python module. It's incredibly simple and concise, e.g.:

    from sh import date, ls, egrep, git

    print date(), ls('~/project')
    print egrep(ls('~/project'), '-o', '\.py$')
    print git.add(egrep(ls('~/project'), '-o', '\.py$'))

[1] http://amoffat.github.io/sh/