[Python-Dev] io.BufferedReader.peek() Behaviour in python3.1

[Cameron Simpson]

On 16Jun2009 11:21, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> Cameron Simpson wrote:
>> It seems like whenever I want to do some kind of opportunistic but
>> non-blocking stuff with a remote service
>
> Do you actually do this with buffered streams?

Sure, in C, python and perl quite happily. In some circumstances.
Provided you're careful about when to fflush() it can all go quite
smoothly. It's certainly not applicable to everything.

> I find
> it's better to steer well clear of buffered I/O objects
> when doing non-blocking stuff, because they don't play
> well with other things like select().

Ah, the non-blockingness. Well that's the rub. I normally avoid
non-blocking requirements by using threads, so that the thread gathering
from the stream can block. Then the consumer can poll a Queue from the
worker thread, etc.

I really don't like select(/poll/epoll etc) much; aside from select's
scaling issues with lots of files (hence poll/epoll) there are high
performance things where having an event loop using select is a good
way to go, but I generally prefer using threads and/or generators
to make the code clear (single flow of control, single task for the
block of code, etc) if there's no reason not to.

> Anyhow, I wouldn't be opposed to having a way of looking
> into the buffer, but it should be a separate API  --
> preferably with a better name than peek0(), which gives
> no clue at all about what it does differently from peek().

Indeed, though arguably read1() is a lousy name too, on the same basis.
My itch is that peek() _feels_ like it should be "look into the buffer"
but actually can block and/or change the buffer.

Cheers,
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

You can't wait for inspiration.  You have to go after it with a club.
        - Jack London