python: calling method over multiple instances parallelly [duplicate]

Answer 1

This code seems to show the difference between a for loop and Pool, calling a method on different instances:

from multiprocessing import Pool

instances = ['a','ab','abc','abcd']


def calc_stuff(i):
    return len(i)


if __name__ == '__main__':

    print('One at a time')
    for i in instances:
        print(len(i))

    print('Use Pool')
    with Pool(4) as pool:
        print(pool.map(calc_stuff, instances))

Note the use of if __name__ == '__main':

This separates each process out.

Output:

One at a time
1
2
3
4
Use Pool
[1, 2, 3, 4]