Concurrency in Python 3

futures.py

# Source: http://firepear.net/docs/python3-futures-2.html

from concurrent.futures import ThreadPoolExecutor
import random
import time

def sleep_until_the_future(**kwargs):
    kwargs['launchtime'] = time.time()
    time.sleep(kwargs['sleeptime'])
    return kwargs

def say_hello_from_the_future(future):
    result = future.result()
    now = time.time()
    actualsleep = now - result['launchtime']
    print("This is future {}.".format(result['futurenum']),
          "I was created at {} and launched at {}.".format(result['createtime'], result['launchtime']),
          "I was told to sleep for {} seconds.".format(result['sleeptime']),
          "I woke up at {},".format(now),
          "so I actually slept for {} seconds.".format(actualsleep))

def main():
    executor = ThreadPoolExecutor(max_workers=10)
    for i in range(20):
        future = executor.submit(sleep_until_the_future,
                                 futurenum=i,
                                 sleeptime=(random.random() * 10),
                                 createtime = time.time())
        future.add_done_callback(say_hello_from_the_future)
    for i in range(20):
        time.sleep(1)
        print("MAIN THREAD. Seconds elapsed: {}".format(i + 1))

if __name__ == "__main__":
    main()