python multiprocessing is not giving output

Question

I just learned about python multiprocessing and was trying to apply it in the following way:

Here this class A is going to run class B which inherits multiprocessing.Process

import multiprocessing as mp

class A:
    def __init__(self, num_workers=mp.cpu_count()):
        self.num_workers = num_workers
        self.x = 5
    
    def process(self):
        workers = []
        for i in range(self.num_workers):
            workers.append(B(self.x))
        for worker in workers:
            worker.start()
        for worker in workers:
            worker.join()

class B(mp.Process):
    def __init__(self, val):
        mp.Process.__init__(self)
        self.val = val
        
    def square(self):
        print(self.val * self.val)
    
    def run(self):
        self.square()

Finally calling the classes to run the square function in this way:

a = A()
a.process()

But I am not getting any output.

Note that this is a dummy micro version of another code which I am trying to convert multi-thread to multiprocessing due to some issue.

Answer 1

Call your classes like so

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

Read Safe importing of main module for more info on why