how to kill (or avoid) zombie processes with subpr

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 kill this subprocess unless I kill my parent python process.

Is there a way to kill the subprocess without killing the parent? I know I can do this by using wait(), but I need to run my script with no_wait().

Answer 1

The python runtime takes responsibility for getting rid of zombie process once their process objects have been garbage collected. If you see the zombie lying around it means you have kept a process object and not called wait, poll or terminate on it.

Answer 2

Recently, I came across this zombie problem due to my python script. The actual problem was mainly due to killing of the subprocess and the parent process doesn't know that the child is dead. So what I did was, just adding popen.communicate() after the kill signal of child process so that the parent process comes to know that the child is dead, then the kernel updates the pid of the childprocess since the child is no more and so there is no zombies formed now.

PS:poll is also an option here since it checks and conveys about the child status to the parent. Often in subprocess it is better if u use check_output or call if u need not communicate with the stdout and stdin.