lesson04_event.py

# SuperFastPython.com
# example of using an event object with threads
from time import sleep
from random import random
from threading import Thread
from threading import Event

# custom function to be executed in a new thread
def task(shared_event, number):
 # wait for the event to be set
 print(f'Thread {number} waiting...')
 shared_event.wait()
 # begin work, generate a random number
 value = random()
 # block for a fraction of a second
 sleep(value)
 # report a message
 print(f'Thread {number} got {value}')

# protect the entry point
if __name__ == '__main__':
 # create a shared event object
 event = Event()
 # create a suite of threads
 threads = [Thread(target=task,
 args=(event, i)) for i in range(5)]
 # start all threads
 for thread in threads:
 thread.start()
 # block thread a moment
 print('Main thread blocking...')
 sleep(2)
 # trigger all threads
 event.set()
 # wait for all threads to terminate
 for thread in threads:
 thread.join()