Python OSError: [Errno 2]

I have the following code that is attempting to start each of the "commands" below in Linux. The module attempts to keep each of the 2 commands running if either should crash for whatever reason.

#!/usr/bin/env python

import subprocess



commands = [ ["screen -dmS RealmD top"], ["screen -DmS RealmD top -d 5"] ]

programs = [ subprocess.Popen(c) for c in commands ]

while True:

    for i in range(len(programs)):

        if programs[i].returncode is None:

            continue # still running

        else:

            # restart this one

            programs[i]= subprocess.Popen(commands[i])

        time.sleep(1.0)

Traceback (most recent call last):

  File "./marp.py", line 82, in <module>

    programs = [ subprocess.Popen(c) for c in commands ]

  File "/usr/lib/python2.6/subprocess.py", line 595, in __init__

    errread, errwrite)

  File "/usr/lib/python2.6/subprocess.py", line 1092, in _execute_child

    raise child_exception

OSError: [Errno 2] No such file or directory