How to terminate a thread in Python without loop in run method?

Question

Having class which has a long method.
Creating a thread for that method.
How i can kill\terminate this thread?
Main problem is that i can't check for threading.Event in thread run() method because it doesn't contain loop.
Similar code as here:

import time
import threading

class LongAction:
    def time_consuming_action(self):
        tmax = 600
        for i in range(tmax):
            print i
            time.sleep(1)
        time.sleep(tmax)
        self.tmax = tmax
        return "Slept well"

class LongActionThread(threading.Thread):
    def __init__(self, la_object):
        self.la = la_object
        threading.Thread.__init__(self)

    def run(self):
        self.la.time_consuming_action()


la = LongAction()
la_thread = LongActionThread(la)
la_thread.start()

# After 5 sec i've changed my mind and trying to kill LongActionThread
time.sleep(5)
print "Trying to kill LongActionThread"
la_thread.kill()

it's not generally a good idea to kill a thread : http://stackoverflow.com/questions/323972/is-there-any-way-to-kill-a-thread-in-python — lucasg, Dec 03 '12 at 11:45
I understand but i need that. Read this link but first example didn't help. I guess then there is only one way - with exception? — ambi, Dec 03 '12 at 11:47
If you might need to kill a task, it's much better to run it in a process than a thread. See the [multiprocessing](http://docs.python.org/2/library/multiprocessing.html) module for example. — Useless, Dec 03 '12 at 12:11
Is your real time_consuming_action in Python? Does it contain a loop where you could insert the event check? — Janne Karila, Dec 03 '12 at 12:27
May be this link useful to you... http://stackoverflow.com/questions/6524459/stopping-a-thread-python — Anup, Dec 03 '12 at 13:14

score 1 · Answer 1 · answered Dec 12 '12 at 11:34

This code works fine but there is a need to explicitly flush data from standard output.
Haven't found a way where prints would work without flushing.

import time
from multiprocessing.process import Process
import sys

class LongAction:
    def time_consuming_action(self):
        tmax = 600
        for i in range(tmax):
            print i
            time.sleep(1)
            sys.stdout.flush()
        time.sleep(tmax)
        self.tmax = tmax
        return "Slept well"
        sys.stdout.flush()

class LongActionThread(Process):
    def __init__(self, la_object):
        self.la = la_object
        Process.__init__(self)

    def run(self):
        self.la.time_consuming_action()

if __name__ == "__main__":
    la = LongAction()
    la_thread = LongActionThread(la)
    la_thread.start()

    # After 5 sec i've changed my mind and trying to kill LongActionThread
    time.sleep(5)
    print "Trying to kill LongActionThread"
    la_thread.terminate()

OP says `time_consuming_action()` can't be changed. – Marichyasana Dec 04 '15 at 11:38 — Marichyasana, Dec 04 '15 at 11:38

score 0 · Answer 2 · edited May 23 '17 at 12:26

While it is not a good idea to kill a thread, if you really must do it, the easiest solution is to implement a running semaphor, divide your time consuming method in sub_methods and check for thread status between the submethods.

Code partly copied from this SO question:

class StoppableThread(threading.Thread):
    """Thread class with a stop() method. The thread itself has to check
    regularly for the stopped() condition."""

    def __init__(self,la_object):
        super(StoppableThread, self).__init__()
        self.la = la_object
        self._stop = threading.Event()

    def stop(self):
        self._stop.set()

    def stopped(self):
        return self._stop.isSet()

    def run(self):
       self.la.time_consuming_action( self.stopped )

    class La :

      def __init__(self):
      #init here

      def time_consuming_action(self, thread_stop_callback ):

          sub_work1()

          if thread_stop_callback():
             raise 'Thread Killed ! '

          sub_work2()

          if thread_stop_callback():
             raise 'Thread Killed ! '

          sub_work3()

          #etc...

Problem is that i can't changed **LongAction** class – ambi Dec 03 '12 at 12:25 — ambi, Dec 03 '12 at 12:25

How to terminate a thread in Python without loop in run method?

2 Answers2

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