docs on for-loop with no __iter__?

[Steven Bethard]

Andrew Dalke <adalke <at> mindspring.com> writes:
> Steven Bethard wrote:
> > Presumably there was a reason not to use len() to determine
> > the end of the sequence?
> 
> Because that allows iteration over things where
> you don't yet know the size.

I'm trying to imagine a situation where it makes sense to want the x[i] 
behavior from __getitem__ but where you don't know the final index.  x[i] 
suggests random access, so if you don't really have random access, shouldn't 
you be defining __iter__ instead?  Are there some good examples of classes 
that allow the x[i] indexing but don't support random access (e.g. you can do 
only do x[2] after you do x[1])?

(Obviously your FileReader class was an example of this, but I've assumed this 
was just an example of how things *could* have been written, not how they 
actually were.  Please correct me if I'm wrong!)

Steve