import subprocess
import os
import signal
import time 

path = os.path.abspath(__file__).rpartition('/')[0]

child_comm = ['python %s/child.py' % path]
parent_comm = ['python %s/parent.py' % path]

proc = subprocess.Popen(child_comm, shell=True)
print 'New child process created'

your_condition = True

while your_condition:
    time.sleep(1)

subprocess.Popen(parent_comm, shell=True, preexec_fn=os.setpgrp)
print 'New wrapper(parent process) created'
print 'Terminating old processgroup...'
os.killpg(os.getpgid(proc.pid), signal.SIGTERM)