04_events.py

import logging
import threading
import time

logging.basicConfig(level=logging.DEBUG,
                    format='(%(threadName)-10s) %(message)s',
                    )


def wait_for_event(e):
    """Wait for the event to be set before doing anything"""
    logging.debug('wait_for_event starting')
    # block until the internal flag is set true!
    event_is_set = e.wait()
    logging.debug('event set: %s', event_is_set)


def wait_for_event_timeout(e, t):
    """Wait t seconds and then timeout"""
    while not e.isSet():
        logging.debug('wait_for_event_timeout starting')
        # block until flag is set or the timeout specified by the arguments
        event_is_set = e.wait(t)
        logging.debug('event set: %s', event_is_set)
        if event_is_set:
            logging.debug('processing event')
        else:
            logging.debug('doing other work')

# Create an event (Flag is False at init)
e = threading.Event()
t1 = threading.Thread(name='block',
                      target=wait_for_event,
                      args=(e,))
t1.start()

t2 = threading.Thread(name='non-block',
                      target=wait_for_event_timeout,
                      args=(e, 2))
t2.start()

logging.debug('Waiting before calling Event.set()')
time.sleep(3)
# Set the flag here!!
e.set()
logging.debug('Event is set')


''' OUTPUT

(block     ) wait_for_event starting
(non-block ) wait_for_event_timeout starting
(MainThread) Waiting before calling Event.set()
(non-block ) event set: False
(non-block ) doing other work
(non-block ) wait_for_event_timeout starting
(MainThread) Event is set
(non-block ) event set: True
(non-block ) processing event
(block     ) event set: True

Process finished with exit code 0


'''