Run command + script as I make changes to file

execute-file-if-modified.py

import os
import sys
import subprocess
import time

def file_is_modified(filename):
    """ Accepts & returns filename if it has been modified """
    previous_st_mtime = 0
    while True:
        st_mtime = os.stat(filename)[8]
        if not st_mtime > previous_st_mtime:
            time.sleep(0.1)
            continue
        previous_st_mtime = st_mtime
        yield filename

def exec_with_file_output(command, filename):
    """ Take command and filename - check if modified, yields output """
    for modified_filename in file_is_modified(filename):
        process = subprocess.Popen([command, modified_filename], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        yield (process.pid, process.communicate())

def print_output_with_seperator(data, count = 40, word = ''):
    """ Output + seperator for pretty print """
    if data:
        print count * '-' + word + count * '-'
        print data

if __name__=="__main__":
    try:
        for output in exec_with_file_output(sys.argv[1], sys.argv[2]):
            pid, stdoutdata, stderrdata = output[0], output[1][0], output[1][1],
            print_output_with_seperator(stdoutdata, word='stdout for pid: %d' % pid)
            print_output_with_seperator(stderrdata, word='stderr for pid: %d' % pid)
    except (IndexError, OSError) as e:
        print 'Supply [command] [filename]\n%s' % e
    except KeyboardInterrupt:
        print 'Exiting...'