Python start multiprocessing without print/logging statements from processes

Question

I am starting two processes via multiprocessing and this is working fine. The only problems which I have are the print and debug statements from these two processes.

The hope is, to use the REPL and start the processes, like in the background. However, I do not get this to run. I always get the debug statements and therefore can't use the REPL anymore. This is how I call the processes:

processes = [
    Process(target=start_viewer, args=()),
    Process(target=start_server, args=(live, amount, fg))
] 

for p in processes:
    p.start()

Any idea on how to "mute" the process, or get them in the background?

Answer 1

If I correct understand you, you want to not show printing from one of processes. You can achieve this by redirect output of the Python Interpreter. Add sys.stdout = open("/dev/null", 'w') to the process which you want to "mute".

Full working example below.

from multiprocessing import Process
from time import sleep
import sys


def start_viewer():
    sys.stdout = open("/dev/null", 'w')
    while True:
        print("start_viewer")
        sleep(1)

def start_server():
    while True:
        print("start_server")
        sleep(1)

if __name__ == '__main__':
    processes = [
        Process(target=start_viewer, args=()),
        Process(target=start_server, args=())
    ]

    for p in processes:
        p.start()

Be aware that /dev/null is like passing prints to nowhere, if you want to save it you can use text file. Also to achieve multi os support you should use os.devnull.