readline() blocks after select() says there's data??

[Sjoerd Mullender]

When select tells you there is something available to read, it doesn't mean
there is a whole line available to read!  It is very well possible that there
is only one character available, but readline may want to read (a lot) more
than that.

Rich Cook wrote:
> 
> At 11:09 PM -0600 3/14/02, Skip Montanaro wrote:
> >     >>    selectables = [theProcess.childerr, theProcess.fromchild]
> >     >>    (input, output, exc) = select.select([],selectables, selectables)
> >     ...
> >
> >     >> It blocks forever waiting for theProcess.childerr.readline(bufsize)
> >     >> to return.  I expect it to block waiting for select.select(); that
> >     >> would not be a problem.  The problem is that select is claiming
> >     >> there's stuff to be read, then when I try to read it, it's not there!
> >     >> How can that be?
> >
> >Based upon the attribute names you are using, I suspect you instantiated
> >os.Popen3 to create theProcess.  These are file objects, not sockets.  I
> >believe select only blocks on sockets.  See the comments about asynchronous
> >file i/o near the bottom of asyncore.py.
> 
> I don't really need select to block.  I just want it to be accurate.
> If it returns a file object in the list of things which are
> available, why should then readline() block on it?
> --
> 
> -Sincerely, Rich Cook 925-784-3077
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