#!/usr/bin/env python
     # encoding: utf-8
     #
     # Copyright (c) 2008 Doug Hellmann All rights reserved.
     #
     """Using a Lock without blocking
     """
     #end_pymotw_header
     
     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.acquire()
             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()