how does a queue stop the thread?

K

kaiix

A simple thread pool example. My question is, since *MyThread.run*
will loop endless, how does the thread know the time to quit? how does
the *queue* notify the thread? is there any shared variables, like a
*lock*?

When I set daemon false, it stays in the loop, not quit any more.
what's the role does the daemon state plays?

code:
----------------------------------------------------------------------------------------
import Queue
import threading

def do_some_thing(x):
print int(x)

class MyThread(threading.Thread):
def __init__(self, queue):
threading.Thread.__init__(self)
self.queue = queue

def run(self):
while True:
params = self.queue.get()
do_some_thing(params)
self.queue.task_done()

q = Queue.Queue()

for i in range(1, 5):
t = MyThread(q)
t.setDaemon(True)
t.start()

for x in range(10):
q.put(x)

q.join()
 
K

Kushal Kumaran

A simple thread pool example. My question is, since *MyThread.run*
will loop endless, how does the thread know the time to quit? how does
the *queue* notify the thread? is there any shared variables, like a
*lock*?

When I set daemon false, it stays in the loop, not quit any more.
what's the role does the daemon state plays?

Take a look at the documentation for the threading module here:
http://docs.python.org/release/2.6/library/threading.html, and the
discussion on daemon vs non-daemon threads here:
http://blog.doughellmann.com/2008/01/pymotw-threading_13.html

Basically, as long as at least one non-daemon thread is still running,
your program will not exit.
 
K

Kushal Kumaran

Take a look at the documentation for the threading module here:
http://docs.python.org/release/2.6/library/threading.html, and the
discussion on daemon vs non-daemon threads here:
http://blog.doughellmann.com/2008/01/pymotw-threading_13.html

Basically, as long as at least one non-daemon thread is still running,
your program will not exit.

And I should have read your mail better. Take a look at the
documentation of the task_done method:
http://docs.python.org/library/queue.html
 
K

kaiix

@kushal, thanks for your replies.

before i wrote the email, i've already read the python docs carefully.
i need the proof from code, i mean python source code. i tried to
prove some of my assumptions that lead the loop quit, and i traced
back to Queue.py, threading.py, dummy_thread.py, now i need some hints
to help me understanding the sample from python source code.
 
J

James Mills

before i wrote the email, i've already read the python docs carefully.
i need the proof from code, i mean python source code. i tried to
prove some of my assumptions that lead the loop quit, and i traced
back to Queue.py, threading.py, dummy_thread.py, now i need some hints
to help me understanding the sample from python source code.

You would need to look into the source code of
python's builtin 'thread' module which is the low-level
threading implementation used by python's 'threading'
module (which is a wrapper atop this).

'threading' aside from everything else it does, really in the
end calls thread.start_new_thread(...)

cheers
James
 
S

Steve

A simple thread pool example. My question is, since *MyThread.run*
will loop endless, how does the thread know the time to quit? how does
the *queue* notify the thread? is there any shared variables, like a
*lock*?

When I set daemon false, it stays in the loop, not quit any more.
what's the role does the daemon state plays?

code:
--------------------------------------------------------------------------- -------------
import Queue
import threading

def do_some_thing(x):
    print int(x)

class MyThread(threading.Thread):
    def __init__(self, queue):
        threading.Thread.__init__(self)
        self.queue = queue

    def run(self):
        while True:
            params = self.queue.get()
            do_some_thing(params)
            self.queue.task_done()

q = Queue.Queue()

for i in range(1, 5):
    t = MyThread(q)
    t.setDaemon(True)
    t.start()

for x in range(10):
    q.put(x)

q.join()

Here's a slightly different example that demonstrates more clearly how
to end each thread.

http://effbot.org/librarybook/queue.htm
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Members online

Forum statistics

Threads
473,792
Messages
2,569,639
Members
45,352
Latest member
SherriePet

Latest Threads

Top