how to kill process and child processes from python?

Another solution if your process is not a process group and you don't want to use psutil, is to run this shell command:

pkill -TERM -P 12345

For instance with

os.system('pkill -TERM -P {pid}'.format(pid=12345))

If the parent process is not a "process group" but you want to kill it with the children, you can use psutil (https://psutil.readthedocs.io/en/latest/#processes). os.killpg cannot identify pid of a non-process-group.

import psutil

parent_pid = 30437   # my example
parent = psutil.Process(parent_pid)
for child in parent.children(recursive=True):  # or parent.children() for recursive=False
    child.kill()
parent.kill()

When you pass a negative PID to kill, it actually sends the signal to the process group by that (absolute) number. You do the equivalent with os.killpg() in Python.