Stopping a Thread in Multithreaded Python code

Question

I am working on multithreading in python i could not achieve to stop individual threads. The code is below. How can i achieve this? Thanks...

from threading import Thread
import threading
import time


class MyThread(threading.Thread):
    def stop(self):
        self.stopped = True
        print ("working")
    stopped=True


def func(argument):
    t = threading.current_thread()
    while not t.stopped:
        print(argument)
        time.sleep(0.5)


a = MyThread(target=func,args=("1",))
b = MyThread(target=func,args=("2",))
c = MyThread(target=func,args=("3",))
d = MyThread(target=func,args=("4",))
a.daemon = True
b.daemon = True
c.daemon = True
d.daemon = True
a.start()
b.start()
c.start()
d.start()

time.sleep(3)
b.stop()
c.stop()
d.stop()

After execution of this code, a thread must be alive and still running the function but all of the threads stop.

donkopotamus · Accepted Answer · 2018-01-24 20:41:38Z

3

Clearly you expect that thread a should not stop as you have not called a.stop(). However, you have a class scoped attribute stopped as well:

class MyThread(threading.Thread):
    def stop(self):
        self.stopped = True
        print ("working")

    # !! this is a class level attribute !!
    stopped=True

Thus, MyThread.stopped is True. When you ask an instance of MyThread for the stopped attribute using self.stopped it will:

first check if the attribute stopped exists on the instance;
else check if the attribute exists on the type MyThread

Thus in your case, MyThread().stopped is always True

edited Jan 24, 2018 at 20:41

answered Jan 24, 2018 at 20:34

donkopotamus

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2 Comments

mustaphos Over a year ago

then, which method should i use?

mrjaso Over a year ago

I think you want to initialize stopped = False in your class definition.

mustaphos · Accepted Answer · 2018-01-24 20:56:08Z

0

I figure it out the solution and wanted to share.

from threading import Thread
import threading
import time


class MyThread(threading.Thread):
    stop = False


def func(argument):
    t = threading.current_thread()
    while True:
        if not t.stop:
            print(argument)
            time.sleep(0.5)


a = MyThread(target=func,args=("1",))
b = MyThread(target=func,args=("2",))
c = MyThread(target=func,args=("3",))
d = MyThread(target=func,args=("4",))
a.start()
b.start()
c.start()
d.start()
time.sleep(3)
b.stop = True
c.stop = True
d.stop = True
time.sleep(3)
b.stop = False

answered Jan 24, 2018 at 20:56

mustaphos

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