lesson06_wait_first.py

# SuperFastPython.com
# example of waiting for the first task to complete
from time import sleep
from random import random
from concurrent.futures import ThreadPoolExecutor
from concurrent.futures import wait
from concurrent.futures import FIRST_COMPLETED

# custom task function executed by a worker thread
def task(number):
 # block for a fraction of a second
 sleep(random())
 # report that the task completed
 print(f'>task {number} is done')
 # return the task number
 return number

# protect the entry point
if __name__ == '__main__':
 # start the thread pool
 with ThreadPoolExecutor(10) as exe:
 # submit tasks and collect futures
 futs = [exe.submit(task, i) for i in range(10)]
 # wait until any task completes
 done,_ = wait(futs, return_when=FIRST_COMPLETED)
 # get the first task to complete
 future = done.pop()
 # get the result from the first task to complete
 result = future.result()
 # report the result
 print(f'Main first result: {result}')