#!/usr/bin/env python3

import sys, time
import concurrent.futures as futures

def waitOnWorkers(fs):
	done, notdone = futures.wait(fs, return_when=futures.ALL_COMPLETED)
	return done.pop().result()

def worker():
	time.sleep(3)
	print("worker done")
	return 42

def main():
	poolSize = 500
	executor = futures.ThreadPoolExecutor(max_workers=poolSize)
	fs = [ executor.submit(worker) for i in range(2) ]
	# Fill the pool with waiters that will rush for the exits at the same time
	waiters = [ executor.submit(waitOnWorkers, fs) for i in range(poolSize)]
	print ("Results")
	count = 1
	for completedWaiter in futures.as_completed(waiters):
		print (count, ' ', completedWaiter.result())
		count += 1

if __name__ == '__main__' : 
	status = main()
	sys.exit(status)