py3k buffered IO - flush() required between read/write?

[Genstein]

Hey all,

Apologies if this is a dumb question (self = Python noob), but under 
py3k is it necessary to flush() a file between read/write calls in order 
to see consistent results?

I ask because I have a case under Python 3.2 (r32:88445) where it does 
appear to be, on both Gentoo Linux and Windows Vista.

I've naturally read http://docs.python.org/py3k/library/io.html and 
http://docs.python.org/py3k/tutorial/inputoutput.html#reading-and-writing-files 
but could find no reference to such a requirement.

PEP 3116 suggested this might not be required in py3k and the 
implementation notes in bufferedio.c state "BufferedReader, 
BufferedWriter and BufferedRandom...share a single buffer...this enables 
interleaved reads and writes without flushing." Which seemed conclusive 
but I'm seeing otherwise.

I have a test case, which is sadly rather long: 
http://pastebin.com/xqrzKr5D It's lengthy because it's autogenerated 
from some rather more complex code I'm working on, in order to reproduce 
the issue in isolation.

Any advice and/or flames appreciated.

All the best,

	-eg.