Queue cleanup

[MRAB]

EW wrote:
[snip]
> So here the P2 thread has ended and gone away but I still have his
> Queue lingering.
> 
> So on a thread I can use is_alive() to check status and use join() to
> clean up but I don't see any analogous functionality for Queues.  How
> do I kill them?  I thought about putting a suicide message on the
> Queue and then C1 would read it and set the variable to None but i'm
> not sure setting the variable to None actually makes the Queue go
> away.  It could just end up sitting in memory unreferenced - and
> that's not good.  Additionally, I could have any number of consumer
> threads reading that Queue so once the first one get the suicide note
> the other consumer threads never would.
> 
> I figure there has to be an elegant way for managing my Queues but so
> far I can't find it.  Any suggestions would be appreciated and thanks
> in advance for any help.
> 
An object will be available for garbage collection when nothing refers
to it either directly or indirectly. If it's unreferenced then it will
go away.

As for the suicide note, if a consumer sees it then it can put it back
into the queue so other consumers will see it and then forget about the
queue (set the variable which refers to the queue to None, or, if the
references are in a list, delete it from the list).