thread join python
''' without join: +---+---+---------------------- main-thread | | | +.................... child-thread(short) +............................. child-thread(long) with join +---+---+-------------***********+### main-thread | | | | +...........join() | child-thread(short) +.................join()...... child-thread(long) with join and daemon thread +-+--+---+-------------***********+### parent-thread | | | | | | +......join() | child-thread(short) | +.................join()...... child-thread(long) +,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, child-thread(long + daemonized) '-' main-thread/parent-thread/main-program execution '.' child-thread execution '#' optional parent-thread execution after join()-blocked parent-thread could continue '*' main-thread 'sleeping' in join-method, waiting for child-thread to finish ',' daemonized thread - 'ignores' lifetime of other threads; terminates when main-programs exits; is normally meant for join-independent tasks --------------------------------------------------------- A simple example, say we have this: ''' def non_daemon(): time.sleep(5) print 'Test non-daemon' t = threading.Thread(name='non-daemon', target=non_daemon) t.start() #Which finishes with: print('Test one') t.join() print('Test two') ''' This will output: Test one Test non-daemon Test two Here the master thread explicitly waits for the t thread to finish until it calls print the second time. Alternatively if we had this: ''' print('Test one') print('Test two') t.join() ''' We'll get this output: Test one Test two Test non-daemon'''
