How to kill a process using the multiprocessing module?

Question

I have a process that is essentially just an infinite loop and I have a second process that is a timer. How can I kill the loop process once the timer is done?

def action():
  x = 0
  while True:
      if x < 1000000:
          x = x + 1
      else:
          x = 0

def timer(time):
  time.sleep(time)
  exit()    

loop_process = multiprocessing.Process(target=action)
loop_process.start()
timer_process = multiprocessing.Process(target=timer, args=(time,))
timer_process.start()

I want the python script to end once the timer is done.

Answer 1

You could do it by using a sharing state between the processes and creating a flag value that all the concurrent processes can access (although this may be somewhat inefficient).

Here's what I'm suggesting:

import multiprocessing as mp
import time

def action(run_flag):
    x = 0
    while run_flag.value:
        if x < 1000000:
            x = x + 1
        else:
            x = 0

    print('action() terminating')


def timer(run_flag, secs):
    time.sleep(secs)
    run_flag.value = False


if __name__ == '__main__':

    run_flag = mp.Value('I', True)

    loop_process = mp.Process(target=action, args=(run_flag,))
    loop_process.start()

    timer_process = mp.Process(target=timer, args=(run_flag, 2.0))
    timer_process.start()

    loop_process.join()
    timer_process.join()

    print('done')