如何缓冲multiprocessing.Process内部和外部函数的所有print（）？

Question

I use multiprocessing for some tasks with multiple print() indicators inside them, so I can see how the process started/worked/ended in cmd. But, some tasks are quicker/slower, so print() order is chaotic. I need to find a way how to show all print() at once at the end of the process.

Simplified example:

from multiprocessing import Process
from time import sleep


def runner(px_id):
    print('Start'+str(px_id))

    if px_id > 1:
        sleep(2)
    elif px_id == 1:
        sleep(5)

    print('Middle'+str(px_id))

    if px_id > 1:
        sleep(2)
    elif px_id == 1:
        sleep(5)

    print('End'+str(px_id))


if __name__ == '__main__':
    px_list = [1, 2, 3]

    for px in px_list:
        p = Process(target=runner, args=(px,))
        p.start()

If I run this code now, I'll receive:

Start1
Start2
Start3
Middle2
Middle3
End2
End3
Middle1
End1

While I need something like:

Start2
Middle2
End2
Start3
Middle3
End3
Start1
Middle1
End1

I still need processes to be async (so can't use join() ) but to print all print() at the end of a process. Grateful for any advice :)

UPD: Using an array for buffering function messages is an OK solution, still need some help with buffering solutions from external functions. I mean, if I use some function inside other function I can't buffer all print() manually, so looking for some more complex solution :)

Answer 1

One option would be to have each instance buffer the output in an internal buffer. then output it at the end. You could have the main thread go and save each started process in an array. then wait on all three to finish and finally go and grab the internal buffer from each process in the array and print them serially.