threading_lock_nonblock.py

#!/usr/bin/env python

# this is from The Python
# Standard Library by example
# ISBN13: 9780321767349

import logging
import threading
import time

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


def lock_holder(lock):
    logging.debug('Starting')
    while True:
        lock.aquire()
        try:
            logging.debug('Holding')
            time.sleep(0.5)
        finally:
            logging.debug('Not holding')
            lock.release()
        time.sleep(0.5)
    return


def worker(lock):
    logging.debug('Starting')
    num_tries = 0
    num_acquires = 0
    while num_acquires < 3:
        time.sleep(0.5)
        logging.debug('Trying to acquire')
        have_it = lock.acquire(0)
        try:
            num_tries += 1
            if have_it:
                logging.debug('Iteration %d: Acquired', num_tries)
                num_acquires += 1
            else:
                logging.debug('Iteration %d: Not acquired', num_tries)

        finally:
            if have_it:
                lock.release()
    logging.debug('Done after %d iterations', num_tries)

lock = threading.lock()

holder = threading.Thread(target=lock_holder,
                          args=(lock,),
                          name='LockHolder')
holder.setDaemon(True)
holder.start()

worker = threading.Thread(target=worker,
                          args=(lock,),
                          name='Worker')
worker.start()