How to know the process status in multiprocessing in the target function?

Question

In the multiprocessing how can I know the status(like its running,killed) of current process and other process ?

My scenario is 2 process are running

process_run = multiprocessing.Process(target=run, name="run")
process_read = multiprocessing.Process(target=read_process, name="read_process")
process_run.start()
process_read.start()
processes = [process_run,process_read]

for p in processes:
    p.join()

Here I want to kill process_read once process_run execution is done.

process_read psudo code looks something like this:

def read_process():
    while True:
        #read the data and print in the terminal
        time.sleep(20)

Here I am using while True so this process will not be terminated (not a good way I know). So here I want the stopping condition like once other process is done kill this process.

Can somebody help ?

Answer 1

Use a multiprocessing.Event to signal the other process.

Demo:

import multiprocessing as mp
import time

def process1(stop_event):           # Each process receives the event
    while not stop_event.is_set():  # Run while event is not set
        print('process1')
        time.sleep(.1)
    print('process1: stop')

def process2(stop_event):           # Each process receives the event
    for i in range(5):
        print('process2:', i)
        time.sleep(.1)
    print('process2: done')
    stop_event.set()                # Signal other process to stop

if __name__ == '__main__':
    funcs = process1, process2
    stop_event = mp.Event()  # Create event and send to each process
    processes = [mp.Process(target=func, args=(stop_event,)) for func in funcs]
    for p in processes:
        p.start()
    for p in processes:
        p.join()

Output:

process1
process2: 0
process1
process2: 1
process1
process2: 2
process1
process2: 3
process1
process2: 4
process1
process2: done
process1: stop