[Tutor] Multiprocessing

[Stephen M Smith]

I am trying to figure out how multiprocessing works for an application I
have.  My methodology is to vigorously read everything I can find on the
subject including examples. I have found an example and modified it a bit.
Here is the code and it works:

 

import concurrent.futures

from multiprocessing import Process, freeze_support

import time

print("starting up")

def do_something(seconds):
    print(f'Sleeping {seconds} second(s)')
    time.sleep(1)
    return f"done sleeping...{seconds} seconds"


if __name__ == '__main__':
    print("about to go")
    freeze_support()
    # Process(target=do_something(1)).start

    with concurrent.futures.ProcessPoolExecutor() as executor:
        # f1 = executor.submit(do_something,1)
        secs = [10,9,8,7,6,5,4,3,2,1]
        results = [executor.submit(do_something, sec) for sec in secs]
        for f in concurrent.futures.as_completed(results):
            print(f.result())

 

 

What I don't get is the output, also pasted below. As you will see the
"starting up" message is displayed 17 times. I cannot begin to understand
how that statement is executed more than once and 17 times makes no sense
either. Thanks in advance for any insight you can provide.

 

starting up

about to go

starting up

starting up

starting up

starting up

Sleeping 10 second(s)

starting up

Sleeping 9 second(s)

starting up

Sleeping 8 second(s)

Sleeping 7 second(s)

starting up

starting up

Sleeping 6 second(s)

Sleeping 5 second(s)

starting up

starting up

Sleeping 4 second(s)

starting up

Sleeping 3 second(s)

Sleeping 2 second(s)

starting up

Sleeping 1 second(s)

starting up

starting up

starting up

starting up

done sleeping...10 seconds

done sleeping...9 seconds

done sleeping...8 seconds

done sleeping...5 seconds

done sleeping...4 seconds

done sleeping...7 seconds

done sleeping...6 seconds

done sleeping...3 seconds

done sleeping...2 seconds

done sleeping...1 seconds

 

Process finished with exit code 0