Python: multiprocessing: Daemon process

Daemon processes are low priority processes, which are mainly used for background processing.

How to make a process as daemon process?

By setting daemon property to True, you can make a process as daemon process.

from multiprocessing import Process
import multiprocessing


def print_data():
    name = multiprocessing.current_process().name
    id = multiprocessing.current_process().pid
    print(name, id)
    print("Is deamon ", multiprocessing.current_process().daemon)

if __name__=="__main__":
    proc1 = Process(name='process1', target=print_data)

    proc1.daemon=True

    proc1.start()
    proc1.join()

    print("Finished")

Output

process1 31619
Is deamon  True
Finished

Python program closes its execution, when no other non-daemon process/thread is alive.

from multiprocessing import Process
import multiprocessing
import time


def print_data():
    name = multiprocessing.current_process().name
    id = multiprocessing.current_process().pid
    print(name, id)

    time.sleep(3)
    print("Is deamon ", multiprocessing.current_process().daemon)

if __name__=="__main__":
    proc1 = Process(name='process1', target=print_data)

    proc1.daemon=True

    proc1.start()
    time.sleep(1)

    print("Finished")

Output

process1 31675
Finished

Observe the output, program terminated without printing second print statement of print_data() method. To make daemon process finish execution, you should call join method.

from multiprocessing import Process
import multiprocessing
import time


def print_data():
    name = multiprocessing.current_process().name
    id = multiprocessing.current_process().pid
    print(name, id)

    time.sleep(3)
    print("Is deamon ", multiprocessing.current_process().daemon)

if __name__=="__main__":
    proc1 = Process(name='process1', target=print_data)

    proc1.daemon=True

    proc1.start()
    proc1.join()

    print("Finished")

Output

process1 31690
Is deamon  True
Finished

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