All example concurrent.futures code is failing with “BrokenProcessPool”

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This was my fault, for two reasons:

  1. The code was un-guarded, i.e no if __name__
  2. The strange looking Traceback was because the file was not saved. Never caused me an issue before, but did in this case.

Correcting both of those fixed the error.

Final test code:

import concurrent.futures

nums = [1,2,3,4,5,6,7,8,9,10]

def f(x):
    return x * x
def main():
    # Make sure the map and function are working
    print([val for val in map(f, nums)])

    # Test to make sure concurrent map is working
    with concurrent.futures.ProcessPoolExecutor() as executor:
        print([val for val in executor.map(f, nums)])

if __name__ == '__main__':
    main()

Output, as expected:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

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