Python multiprocessing.Pool workers remain idle

Question

I am a beginner with Python. I am trying to run a simple function using multiprocessing.Pool, but when I run the program, it does not get processed. I can see that distinct processes are spawned, but that they remain idle . For example, the code below does does generate two worker processes but no output and nothing else:

import multiprocessing

def f(x):
    print("Process "+str(x))
    return True

if __name__ == '__main__':
    pool = multiprocessing.Pool(processes=2)            
    result = pool.map(f, range(1000)) 

I am running Python 3.9 using Microsoft Visual Studio 2019. OS is Windows 10. I encountered the same problem using Python 3.7 on this computer. I have tried the same code on another computer (Also Windows 10, VS2019) and it works fine. The difference is that this one has an i9 Processor , while the other has an i7.

I have searched online, but I have not encountered any similar issue or any fix for my problem. Does anyone have any idea why does this happen and/or possible fixes? May the type of processor have something to do with it? Thanks!

Answer 1

This is a just a guess:

I know that this will not run under Jupyter Notebook or the interactive interpreter. See the multiprocessing docs , in particular the section:

The solution for those environments is to take your worker function, f , and place it in a separate module, for example worker.py , and to import the worker function:

import multiprocessing
from worker import f

if __name__ == '__main__':
    pool = multiprocessing.Pool(processes=2)
    result = pool.map(f, range(1000))          

Give this a shot and let us know for others who also have Visual Studio whether this worked or not. Thanks.