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Date: Thu, 15 Aug 2013 09:19:52 -0700
From: Jack Bates <tdhfwh@nottheoilrig.com>
To: Antoine Pitrou <solipsis@pitrou.net>
Subject: Re: Pair of filenos read/write each other?
References: <mailman.552.1376435986.1251.python-list@python.org> <pan.2013.08.14.07.21.36.218000@nowhere.com> <loom.20130814T102738-513@post.gmane.org>
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On Wed, Aug 14, 2013 at 08:34:36AM +0000, Antoine Pitrou wrote:
> Nobody <nobody <at> nowhere.com> writes:
> > On Tue, 13 Aug 2013 16:10:41 -0700, Jack Bates wrote:
> > > Is there anything like os.pipe() where you can read/write both ends?
> > 
> > There's socket.socketpair(), but it's only available on Unix.
> > 
> > Windows doesn't have AF_UNIX sockets, and anonymous pipes (like the ones
> > created by os.pipe()) aren't bidirectional.
> 
> I'm not sure I understand the problem: you can just create two pair of pipes
> using os.pipe().
> If that's too low-level, you can wrap the fds using BufferedRWPair:
> http://docs.python.org/3.3/library/io.html#io.BufferedRWPair
> 
> (actual incantation would be:
>  r1, w1 = os.pipe()
>  r2, w2 = os.pipe()
> 
>  end1 = io.BufferedRWPair(io.FileIO(r1, 'r'), io.FileIO(w2, 'w'))
>  end2 = io.BufferedRWPair(io.FileIO(r2, 'r'), io.FileIO(w1, 'w'))
> 
>  end1.write(b"foo")
>  end1.flush()
>  end2.read(3)  # -> return b"foo"
> )
> 
> An alternative is to use multiprocessing.Pipe():
> http://docs.python.org/3.3/library/multiprocessing.html#multiprocessing.Pipe
> 
> In any case, Python doesn't lack facilities for doing what you want.

Thank you for your help, I need to satisfy an interface that requires a single
file descriptor number that can be both read from and written to. Is it
possible with any of the solutions you pointed out to get a single file
descriptor number for each end?