ValueError: 'Pool not running' when trying to loop the multiprocessing pool

Question

I'm trying to run the same pool three times so that it adds the values in the same list:

import multiprocessing

def foo(name,archive):
    print('hello ', name)
    archive.append(f"hello {name}")

def main():
    max_process = multiprocessing.cpu_count()-1 or 1
    pool = multiprocessing.Pool(max_process)
    manager = multiprocessing.Manager()

    archive = manager.list()

    arguments = ['home','away','draw']
    for _ in range(3):
        [pool.apply_async(foo, args=[name,archive]) for name in arguments]
        pool.close()
        pool.join()
    print(archive)

if __name__ == '__main__':
    main()

The first batch runs perfectly, but when the second batch goes, this error appears:

ValueError: Pool not running

How should I proceed to generate this looping?

Answer 1

As indicated by Nullman in comments, the error was in keeping pool.close() and pool.join() inside the loop, bringing them out, worked perfectly:

import multiprocessing

def foo(name,archive):
    print('hello ', name)
    archive.append(f"hello {name}")

def main():
    max_process = multiprocessing.cpu_count()-1 or 1
    pool = multiprocessing.Pool(max_process)
    manager = multiprocessing.Manager()

    archive = manager.list()

    arguments = ['home','away','draw']
    for _ in range(3):
        [pool.apply_async(foo, args=[name,archive]) for name in arguments]
    pool.close()
    pool.join()
    
    print(archive)

if __name__ == '__main__':
    main()