Python how to do multiprocessing inside of a class?

Question

I have a code structure that looks like this:

Class A:
  def __init__(self):
    processes = []
    for i in range(1000):
      p = Process(target=self.RunProces         


        

Answer 1

There are a couple of syntax issues that I can see in your code:

• args in Process expects a tuple, you pass an integer, please change line 5 to:

  p = Process(target=self.RunProcess, args=(i,))

• list.append is a method and arguments passed to it should be enclosed in (), not [], please change line 6 to:

  processes.append(p)

As @qarma points out, its not good practice to start the processes in the class constructor. I would structure the code as follows (adapting your example):

import multiprocessing as mp
from time import sleep

class A(object):
    def __init__(self, *args, **kwargs):
        # do other stuff
        pass

    def do_something(self, i):
        sleep(0.2)
        print('%s * %s = %s' % (i, i, i*i))

    def run(self):
        processes = []

        for i in range(1000):
            p = mp.Process(target=self.do_something, args=(i,))
            processes.append(p)

        [x.start() for x in processes]


if __name__ == '__main__':
    a = A()
    a.run()