Newbie prob: How to write a file with 3 threads?

[est]

On May 8, 2:13 pm, Dennis Lee Bieber <wlfr... at ix.netcom.com> wrote:
> On 7 May 2007 18:22:07 -0700, est <electronix... at gmail.com> declaimed
> the following in comp.lang.python:
>
>
>
> > I guess I will write multiple files, one thread one file, and after
> > all threads terminates, I combine the files. That's a cheaper
> > solution, I think.
>
>         Given your first description:
>
> > I need to write a file using 3 threads simutaniously, e.g. Thread 1
> > write the first byte of test.bin with an "a", second thread write the
> > second byte "b", third thread write the third byte "c". Anyone could
> > give a little example on how to do that?
>
> ... any other solution may not have worked anyway. That is, if you
> really expect the three threads to interleave their output as
> abcabcabcabc. If threading, you have no assurance that any single thread
> will follow any other during a task switch. It all depends upon where a
> task switch takes place.
>
>         But then, your example isn't too clear of what you really are
> producing for output. If, instead of "bytes", you meant that each thread
> was writing logging information, the solution would be to use the
> logging module -- so far as I know, the logging module /does/ perform
> the needed access locking.
>
>         OTOH, if you really mean to have three separate byte producers,
> interleaving output, the only safe way would be to have /each/ have an
> output Queue, and a fourth thread doing the writing using a loop of the
> form:
>
> while True:
>         a = aQueue.get()
>         fout.write(a)
>         b = bQueue.get()
>         fout.write(b)
>         c = cQueue.get()
>         fout.write(c)
>
>         Using the separate queues means that the writer WILL wait until the
> next producer in the interleave has produced its data. Of course, this
> structure has the drawback that all producers must produce the same
> amount of data -- otherwise it blocks forever on the queue from the
> producer has stopped generating data.
> --
>         Wulfraed        Dennis Lee Bieber               KD6MOG
>         wlfr... at ix.netcom.com             wulfr... at bestiaria.com
>                 HTTP://wlfraed.home.netcom.com/
>         (Bestiaria Support Staff:               web-a... at bestiaria.com)
>                 HTTP://www.bestiaria.com/

I'd like to say VERY VERY VERY thank you for your detailed
information, that's a lot encourage for a beginner. In fact I am
writing a multi thread download ultility, and I found that very hard
for me. Can you recommand any sample code where I can start with? I
hope I can catch up with everyone here, I'll try my best learning
python. Thank you again.