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Stopping a thread from the calling process

Gordon McMillan gmcm at hypernet.com
Mon Jan 17 08:42:42 EST 2000 
P.J.W.S. Vrijlandt wrote:

> Gordon wrote:
> 
> > The normal idiom is to ask politely - have the thread 
> > periodically check some variable to see if it should stop.
> 
> How would you do this if the thread-to-be-stopped is waiting for 
> (keyboard-) input?
> 
> e.g. in telnetlib we have:
> 
>     def mt_interact(self):
>         """Multithreaded version of interact()."""
>         import thread
>         thread.start_new_thread(self.listener, ())
>         while 1:
>             line = sys.stdin.readline()
>             if not line:
>                 break
>             self.write(line)
> 
>     def listener(self):
>         """Helper for mt_interact() -- this executes in the other  
>         thread."""         
>         while 1:                        
>             try:
>                 data = self.read_eager()
>             except EOFError:
>                 print '*** Connection closed by remote host ***'
>                 return
>             if data:
>                 sys.stdout.write(data)
>             else:
>                 sys.stdout.flush()
> 
> mt_interact should break out of its loop when EOFError occurs within 
> listener.
> 
> (also note that select on input won't work on win32, and looping on 
> keypressed seems rather processor-unfriendly)

Well, select (if it worked on files on WIn32) would be optimal.

Using busy-wait is somewhat offensive, but
 if not msvcrt.kbhit():
   time.sleep(0.1)
is not going to consume much CPU.

If EOF on the socket is the end of the program, I would 
reverse the purpose of the threads, (have the worker thread 
read stdin).
 
> BTW: Would this be better rewritten (for this reason or another) 
> using threading? 

Glancing at it (I've never used it), it looks like there should 
probably be a condition protecting use of the socket; so 
probably yes.



- Gordon
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