CODEWITHSUNDEEP
pythonmultithreading
damon
damon

Reputation: 8477

experimenting with python threads, how to stop thread

watching David beazley's(http://www.dabeaz.com) video about python threads,I was trying out stuff with threads

def countdown(n):
    while n > 0:
        if not  n % 100000:
            print n
        n -= 1

>> from threading import Thread
>> t1=Thread(target=countdown,args=(10000000,))
>> t1.start();t1.join()
>>Ctrl-C

this gave

>>10000000
9900000
9800000
9700000
9600000
Ctrl-C9500000
9400000
...
400000
300000
200000
100000
----------
KeyboardInterrupt :
...

Now I tried to find the status of the thread

>>t1.isAlive()
>>False

So,I tried to run the thread again, which caused an error

>>t1.start();t1.join()
--------------
RuntimeError: thread already started

Why does this happen? is there a way to stop the thread?

Upvotes: 2

Views: 237

Answers (2)

0x434D53
0x434D53

Reputation: 1463

Python3 did repair the behaviour a little: You get an "thread can only be started once". This is by design.

If you want to have more control you may have a look at the _thread module, which is just a wrapper on the POSIX threads.

Upvotes: 2

Patashu
Patashu

Reputation: 21793

In the thread library you are using, a given instance of a thread can only be started and stopped once, and thereafter not started again. The error message you got was because you tried to start a thread after it had gotten stopped, so you did succeed in stopping it. To 'start the thread again' you must instantiate a brand new thread and start that instead.

Upvotes: 4

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