On Wed, 18 Feb 2009 at 21:25, Antoine Pitrou wrote:
Nick Coghlan <ncoghlan <at> gmail.com> writes:
I *think* the 2.x system had an internal buffer that was used by the
file iterator, but not by the file methods. With the new IO stack for
3.0, there is now a common buffer shared by all the file operations
(including iteration).
However, given that the lifting of the restriction is currently
undocumented, I wouldn't want to see a commitment to keeping it lifted
until we know that it won't cause any problems for the io-in-c rewrite
for 3.1 (hopefully someone with more direct involvement with that
rewrite will chime in, since they'll know a lot more about it than I do).
As you said, there is no special buffering for the file iterator in 3.x, which
means the restriction could be lifted (actually there is nothing relying on this
restriction in the current code, except perhaps the "telling" flag in
TextIOWrapper).
Currently I have python (2.x) code that uses 'readline' instead of 'for
x in myfile' in order to avoid the 'for' buffering (ie: be presented
with the next line as soon as it is written to the other end of a pipe,
instead of waiting for the buffer to fill). Does "no special buffering"
mean that 'for' doesn't use a read-ahead buffer in p3k, or that readline
does use such a buffer, because the latter could make my code break
unexpectedly when porting to p3k.
--RDM
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