thread join python

1'''
2without join:
3+---+---+----------------------            main-thread
4    |   |
5    |   +....................              child-thread(short)
6    +.............................         child-thread(long)
7
8with join
9+---+---+-------------***********+###      main-thread
10    |   |                        |
11    |   +...........join()       |         child-thread(short)
12    +.................join()......         child-thread(long)
13
14with join and daemon thread
15+-+--+---+-------------***********+###     parent-thread
16  |  |   |                        |
17  |  |   +......join()            |        child-thread(short)
18  |  +.................join()......        child-thread(long)
19  +,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,     child-thread(long + daemonized)
20
21'-' main-thread/parent-thread/main-program execution
22'.' child-thread execution
23'#' optional parent-thread execution after join()-blocked parent-thread 
24	could 
25    continue
26'*' main-thread 'sleeping' in join-method, waiting for child-thread to 
27	finish
28',' daemonized thread - 'ignores' lifetime of other threads;
29    terminates when main-programs exits; is normally meant for 
30    join-independent tasks
31    
32---------------------------------------------------------
33
34A simple example, say we have this:
35'''
36def non_daemon():
37    time.sleep(5)
38    print 'Test non-daemon'
39
40t = threading.Thread(name='non-daemon', target=non_daemon)
41
42t.start()
43#Which finishes with:
44
45print('Test one')
46t.join()
47print('Test two')
48
49'''
50This will output:
51
52Test one
53Test non-daemon
54Test two
55Here the master thread explicitly waits for the t thread to finish until it calls print the second time.
56
57Alternatively if we had this:
58'''
59
60print('Test one')
61print('Test two')
62t.join()
63'''
64We'll get this output:
65
66Test one
67Test two
68Test non-daemon'''