Right now you can use subprocess.Popen.communicate() to
make communication with subprocesses much easier and
less likely to block than communicating directly with
.stdin, .stdout, etc.  However, that requires
completely buffering the input and output.

The functionality of communicate() (which is somewhat
complex because of platform issues) could be made more
general fairly easily.  The current functionality of
communicate could then be implemented in terms of that
new method.

I attached a function I'm using which does that for the
posix systems (basically turning Popen's posix
communicate into a function with some modifications). 
Replace "proc" with "self" (and give the function a
better name) and you'd have a method.

If patch 1175984 was accepted, then this wouldn't be
that much of an issue:
http://sourceforge.net/tracker/index.php?func=detail&aid=1175984&group_id=5470&atid=305470