running two process simultaneously

Question

I'm trying to run 2 processes simultaneously, but only the first one runs

def add():
    while True:
        print (1)
        time.sleep(3)

def sud():
     while True:
        print(0)
        time.sleep(3)

p1 = multiprocessing.Process(target=add) 
p1.run()
p = multiprocessing.Process(target=sud)
p.run()

Oh hey, it's this bug again. The `start`/`run` name choices have caused so many headaches over the years. — user2357112, Aug 31 '16 at 20:41
@jpmc26: Likely, but I didn't find one in a quick search for `Python multiprocessing start run`. — user2357112, Aug 31 '16 at 21:18
@user2357112 Found one that has an answer describing the difference: [Python multiprocessing.Process: start with local variable](http://stackoverflow.com/questions/32703083/python-multiprocessing-process-start-with-local-variable). Or maybe we need a better written/flushed out one? — jpmc26, Aug 31 '16 at 21:19

Brij · Accepted Answer · 2016-08-31T23:09:48.373

Below will work for sure but try to run this as a module.Don't try in console or Jupiter notebook as notebook will never satisfy the condition "if name == 'main'". Save the entire code in a file say process.py and run it from command prompt. Edit - It's working fine. Just now I tried -

import multiprocessing
import time
def add():
    while True:
        print (1)
        time.sleep(3)

def sud():
     while True:
        print(0)
        time.sleep(3)
if __name__ == '__main__':
    p1 = multiprocessing.Process(name='p1', target=add)
    p = multiprocessing.Process(name='p', target=sud)
    p1.start()
    p.start()

score 3 · Answer 2 · answered Aug 31 '16 at 20:43

3

The method you're looking for is start, not run. start starts the process and calls run to perform the work in the new process; if you call run, you run the work in the calling process instead of a new process.

answered Aug 31 '16 at 20:43

user2357112

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start() does nothing. – aja Aug 31 '16 at 20:45
@YashwantSingh: Are you on Windows? If so, `start` seems to do nothing because you have another bug: you didn't use an `if __name__ == '__main__'` guard, which is mandatory to use `multiprocessing` on Windows due to a lack of `fork`. – user2357112 Aug 31 '16 at 20:46
@YashwantSingh: Then there must be a problem in some part of your code or your development environment that you haven't shown us. – user2357112 Aug 31 '16 at 20:59
I've edited the code pls see to it, this time with start(), but still only first one executes. using Windows , anaconda – aja Aug 31 '16 at 21:04
@YashwantSingh: I don't see the edit you're referring to. – user2357112 Aug 31 '16 at 21:05
@YashwantSingh: Why did you move the process creation and `start` calls into `add` and `sud`? – user2357112 Aug 31 '16 at 21:09
because nothing was happening in main() – aja Aug 31 '16 at 21:10
Well, you've screwed up your code in yet another way by doing that. – user2357112 Aug 31 '16 at 21:11
I'm rolling the code back to its original form, since the new version is wrong in an entirely different way that belongs in a new question. – user2357112 Aug 31 '16 at 21:15
@user2357112 I don't think the new version would be a good question, either. – jpmc26 Aug 31 '16 at 21:18

running two process simultaneously

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