how to kill (or avoid) zombie processes with subprocess module

Question

When I kick off a python script from within another python script using the subprocess module, a zombie process is created when the subprocess \"completes\". I am unable to

Answer 1

I'm not sure what you mean "I need to run my script with no_wait()", but I think this example does what you need. Processes will not be zombies for very long. The parent process will only wait() on them when they are actually already terminated and thus they will quickly unzombify.

#!/usr/bin/env python2.6
import subprocess
import sys
import time

children = []
#Step 1: Launch all the children asynchronously
for i in range(10):
    #For testing, launch a subshell that will sleep various times
    popen = subprocess.Popen(["/bin/sh", "-c", "sleep %s" % (i + 8)])
    children.append(popen)
    print "launched subprocess PID %s" % popen.pid

#reverse the list just to prove we wait on children in the order they finish,
#not necessarily the order they start
children.reverse()
#Step 2: loop until all children are terminated
while children:
    #Step 3: poll all active children in order
    children[:] = [child for child in children if child.poll() is None]
    print "Still running: %s" % [popen.pid for popen in children]
    time.sleep(1)

print "All children terminated"

The output towards the end looks like this:

Still running: [29776, 29774, 29772]
Still running: [29776, 29774]
Still running: [29776]
Still running: []
All children terminated