Multithread Python exit

Question

I have an API and I want to create a client to send/recv data from the interne, so I used a thread so my api won't freeze because of the blocking commands. In my thread I loop while I write/read data. Problem is that after 1 loop program exits and I don't know why.

here is my thread class

class WorkerThread(Thread):
"""Worker Thread Class."""
def __init__(self):
    """Init Worker Thread Class."""
    Thread.__init__(self)
    self._want_abort = 0
    # This starts the thread running on creation, but you could
    # also make the GUI thread responsible for calling this
    self.start()

def run(self):
    while(1):
        if self._want_abort:
           # Use a result of None to acknowledge the abort (of
            # course you can use whatever you'd like or even
            # a separate event type)
            wx.PostEvent(ResultEvent(None))
            return
        Socket_ID=OPEN_CLIENT(str('184.106.153.149'), 3000, 80, SOCKET_STREAM)

        WRITE(Socket_ID, 123, len(123))
        time.sleep(0.5)
        test = READ(Socket_ID)
        if 'on' in test:
            SET_IO(1,1)
        if 'off' in test:
            SET_IO(1,0)

        time.sleep(1)
        CLOSE(Socket_ID)
        time.sleep(10)


def abort(self):
    """abort worker thread."""
    # Method for use by main thread to signal an abort
    self._want_abort = 1

And I call it inside my main after i trigger a checkbox event:

def receive_data(self, event):
        if self.get_cmd == 0:

            self.get_cmd = 1
            self.worker = WorkerThread(self)

        else:
            self.get_cmd = 0
            self.worker.abort()

I saw the Thread class from here: http://wiki.wxpython.org/LongRunningTasks

If I use this, the I/O between client server is OK but API is getting frozed

def receive_data(self, event):
        if self.get_cmd == 0:

            self.get_cmd = 1
            self.worker = WorkerThread(self)
            self.worker.join()

        else:
            self.get_cmd = 0
            self.worker.abort()

Ok, here is another approch that loops 3-4 times and then it crushes:

def receive_data(self, event):

        if self.get_cmd == 0:
            self.thingspeak = threading.Thread(target=recv_data_thingspeak, args = (self.talkback_field.GetValue(),))
            self.thingspeak.start()

        else:
            self.receive_bt.SetValue(True)



def recv_data_thingspeak(queue):

    Socket_ID =OPEN_CLIENT(str('184.106.153.149'), 3000, 80, SOCKET_TYPE_STREAM)
    while(1):

        request = "GET /apps/thinghttp/send_request?api_key=" + queue + " HTTP/1.1\r\n"
        request += "Host: api.thingspeak.com\r\n\r\n"

        WRITE(Socket_ID, 123, len(123))
        time.sleep(1)
        test = READ(Socket_ID)
        if 'on' in test:
            SET_IO(1,1)
        if 'off' in test:
            SET_IO(1,0)

        time.sleep(10)

    CLOSE(Socket_ID)

you should use printouts or a pygdb inside your loop to check why this is exiting. Given your code, it's hard to tell what could cause it to stop after one iteration of the loop. Though your code looks odd to me: you're setting up the thread, then you're joining it back to the main thread right away. — zmo
– zmo, Commented May 21, 2014 at 12:06

johntellsall · Accepted Answer · 2014-05-26 18:45:17Z

Multiple threads can be confusing. For example, in the first batch of code the parent htread is setting (workerthread)._want_abort. However this flag only exists in the parent, not in the worker, so this type of signalling doesn't work.

Generally multithreaded programs work by creating a Queue (or Event, etc) in the parent, then creating a bunch of workers -- giving each one a reference to the Queue. Then when the parent or worker uses the Queue, all threads see the result. You can't do this with a list or other "primitive" object; the Queue has magic so that multiple threads can modify it, and the others will be informed

In the following we start three workers, wait a second, then signal them all to die. We do this by creating an Event in the parent, and sharing it with each worker.

import time
from threading import *

class WorkerThread(Thread):
    def __init__(self, die_flag, *args, **kw):
        super(WorkerThread,self).__init__(*args, **kw)
        self.die_flag = die_flag

    def run(self):
        for num in range(3):
            if self.die_flag.is_set():
                print "{}: bye".format(
                    current_thread().name
                    )
                return
            print "{}: num={}".format(
                current_thread().name, num,
                )
            time.sleep(1)

flag = Event()

print 'STARTING THREADS'
WorkerThread(name='whiskey', die_flag=flag).start()
WorkerThread(name='syrup', die_flag=flag).start()
WorkerThread(name='bitters', die_flag=flag).start()

print '\nRELAXING'
time.sleep(2)

print '\nTELL WORKERS TO DIE'
flag.set()

print '\nWAITING FOR WORKERS'
for thread in enumerate():
    if thread != current_thread():
        print thread.name,':',
        thread.join()
        print 'joined'

print '\nDONE'

Sample run:

STARTING THREADS
whiskey: num=0
syrup: num=0
bitters: num=0

RELAXING
syrup: num=1
whiskey: num=1
bitters: num=1
syrup: num=2
bitters: num=2

TELL WORKERS TO DIE
 whiskey: num=2

WAITING FOR WORKERS
whiskey : joined
bitters : joined
syrup : joined

DONE

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