Why my code is running from the beginning infinitely while it should not?

Question

I have two functions that are going to do something. I need them to run simultaneously until the except case happen, so I have used multiprocessing but whenever I execute my code, it runs from beginning of the code infinitely which there is a few line of code and then my two functions. My code looks something like this:

'''
few line of code
'''


def func_1():
    # Do Somthing


def func_2():
    # Do Somthing


while True:
    try:
        if __name__ == '__main__':
            sensor_process = Process(target=sensor)
            sensor_process.start()
            balance_process = Process(target=balance_fun)
            balance_process.start()
    except(KeyboardInterrupt, SystemExit):
        break

Is there anything wrong with my multiprocessing that my code executes from the beginning infinitely or the problem is somewhere else?

Answer 1

There are some points on your code. First, if you want to execute multiple functions it doesn't mean to create multiple processes each time as you currently doing. You only need one process or thread per function. Second I assume you want your functions run simultaneously forever so you need to put the infinite loop inside each function.

from time import sleep
from multiprocessing import Process


def func_1():
    # Do Somthing
    while True:
        print("hello from func_1")
        sleep(1)

def func_2():
    # Do Somthing
    while True:
        print("hello from func_2")
        sleep(1)

if __name__ == '__main__':
    try:
        sensor_process = Process(target=func_1)
        sensor_process.start()
        balance_process = Process(target=func_2)
        balance_process.start()
        # if you set a control (flag) on both func_1 and func_2 then these two lines would wait until those flags released
        sensor_process.join()
        balance_process.join()
    except(KeyboardInterrupt, SystemExit):
        pass

Answer 2

I think you meant to do something like this:

from multiprocessing import Process

def sensor():
    # Do Somthing
    pass

def balance_fun():
    # Do Somthing
    pass

if __name__ == '__main__':
    try:
        function_list = [sensor, balance_fun] 
        process_list = list()
        for function in function_list:
            proc = Process(target=function)
            proc.start()
            process_list.append(proc)
        for proc in process_list:
            proc.join()
    except(KeyboardInterrupt, SystemExit):
        pass

This will run each function in a separate process and wait for both processes to finish before exiting. Also, if you add more functions, you just need to add them to function_list instead of copying and modifying a block of code.

Answer 3

put a sleep for the main process to get your keyboard interrupt:

while True:
    try:
        if __name__ == '__main__':
            sensor_process = Process(target=sensor)
            sensor_process.start()
            balance_process = Process(target=balance_fun)
            balance_process.start()

        time.sleep(1)

    except(KeyboardInterrupt, SystemExit):
        break

besides, I think creating new processes in an infinite loop is not a good practice.