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From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: Multiple threads
Date: Wed, 16 Nov 2011 16:38:09 -0800
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On Wed, 16 Nov 2011 17:45:29 +0100, Thomas Rachel
<nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de>
declaimed the following in gmane.comp.python.general:

> Am 16.11.2011 14:48 schrieb Eduardo Oliva:
> > Hello, I have a py script that reads for all "m2ts" video files and convert them to "mpeg" using ffmpeg with command line.
> >
> > What I want to do is:
> >
> >    I need my script to run 2 separated threads, and then when the first has finished, starts the next one....but no more than 2 threads.
> >    I know that Semaphores would help with that.
> >    But the problem here is to know when the thread has finished its job, to release the semaphore and start another thread.
> >
> > Any help would be great.
> 
> I'm not sure if you need threads at all: if you launch a process with 
> subprocess, it runs and you only would have to wait() for it. The same 
> can be done with two processes.
>
	In the larger problem description, though, it is mentioned that the
actual conversion is done by spawning an "ffmpeg" command... So why run
a Python process whose only activity is to spawn a process that does the
real work.


	Using a pair (or however many) worker threads which feed off a
shared Queue for the files to convert, and then spawn the ffmpeg
process(es) and wait, is likely simpler than trying to feed data to
external processes.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/