[Python-bugs-list] [ python-Bugs-793687 ] runnig thread multiple times

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Bugs item #793687, was opened at 2003-08-23 19:09
Message generated for change (Comment added) made by spiv
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=793687&group_id=5470

Category: Threads
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Grzegorz Makarewicz (makaron)
Assigned to: Nobody/Anonymous (nobody)
Summary: runnig thread multiple times

Initial Comment:
Internal variable __started remains set to True/1 even
if thread is already terminated, this situation will
generate assertion error when .start is invoked second
time.

demo.py

import time
import threading

done = threading.Event()
def demo():
	print 'bip'
	done.set()

t=threading.Thread(target=demo)
t.start()
while not done.isSet():
	time.sleep(0.1)
done.clear()
print 'returned'
t.start()


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Comment By: Andrew Bennetts (spiv)
Date: 2003-08-29 23:07

Message:
Logged In: YES 
user_id=50945

Also, how would 'someThread.join()' work if threads could be
restarted?

The current situation seems fine to me -- I can't think of a
use-case for this that isn't satisfied by either having an
idiomatic worker thread, or just simply creating a
completely new thread.

Presumably the rationale for wanting restartable threads is
performance, i.e. avoiding setup/teardown costs of threads
-- but this goal is better served by typical worker threads
blocking on a Queue.Queue anyway, i.e.:

    def worker(queue):
         while 1:
             job = queue.get()
             # ...

     q = Queue.Queue()
     t = threading.Thread(target=worker)

In my opinion, the current situation is fine and this
proposal isn't carefully thought out, so thsi bug can be
resolved as "won't fix".

[I seem to recall a bug very similar to this being rejected,
but I can't find it now]

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Comment By: Christos Georgiou (tzot)
Date: 2003-08-29 19:07

Message:
Logged In: YES 
user_id=539787

This is documented behaviour, therefore not a bug (see 
http://www.python.org/doc/current/lib/thread-objects.html , 
doc for the start() method).

The designed methodology is to create a new 
threading.Thread object to start a new thread.

Why re-start a thread anyway?  Optimisation of resources?  
IMHO that would be minor, if existant at all.

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