How to synchronize threads in python?

Question

I have two threads in python (2.7). I start them at the beginning of my program. While they execute, my program reaches the end and exits, killing both of my threads before waiting for resolution.

I'm trying to figure out how to wait for both threads to finish before exiting.

def connect_cam(ip, execute_lock):
    try:
        conn = TelnetConnection.TelnetClient(ip)
        execute_lock.acquire()
        ExecuteUpdate(conn, ip)
        execute_lock.release()
    except ValueError:
        pass


execute_lock = thread.allocate_lock()
thread.start_new_thread(connect_cam, ( headset_ip, execute_lock ) )
thread.start_new_thread(connect_cam, ( handcam_ip, execute_lock ) )

In .NET I would use something like WaitAll() but I haven't found the equivalent in python. In my scenario, TelnetClient is a long operation which may result in a failure after a timeout.

score 4 · Accepted Answer · answered Nov 14 '11 at 20:53

4

Thread is meant as a lower level primitive interface to Python's threading machinery - use threading instead. Then, you can use threading.join() to synchronize threads.

Other threads can call a thread’s join() method. This blocks the calling thread until the thread whose join() method is called is terminated.

answered Nov 14 '11 at 20:53

Aphex

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Yeah, I created a new class inheriting from threading.Thread instead of calling a single function with thread.start_new_thread() – Eric Nov 14 '11 at 21:32

score 4 · Answer 2 · answered Nov 15 '11 at 01:47

Yoo can do something like that:

import threading

class connect_cam(threading.Thread):

    def __init__(self, ip, execute_lock):
        threading.Thread.__init__(self)
        self.ip = ip
        self.execute_lock = execute_lock

    def run(self):
        try:
            conn = TelnetConnection.TelnetClient(self.ip)
            self.execute_lock.acquire()
            ExecuteUpdate(conn, self.ip)
            self.execute_lock.release()
        except ValueError:
            pass


execute_lock = thread.allocate_lock()
tr1 = connect_cam(headset_ip, execute_lock)
tr2 = connect_cam(handcam_ip, execute_lock)
tr1.start()
tr2.start()
tr1.join()
tr2.join()

With the method .join(), the two threads (tr1 and tr2) will wait for each other.

score 2 · Answer 3 · answered Nov 14 '11 at 20:53

2

First, you ought to be using the threading module, not the thread module. Next, have your main thread join() the other threads.

answered Nov 14 '11 at 20:53

ʇsәɹoɈ

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How to synchronize threads in python?

3 Answers3

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