[Python-Dev] Single- vs. Multi-pass iterability

[Alex Martelli]

On Wednesday 17 July 2002 06:40 pm, Guido van Rossum wrote:
	...
> > The file object, unless you make it into an iterator, is not "a
> > container" like all others and just sits there -- a bit of a wart.
>
> I must be misunderstanding.  How does making the file object into an
> iterator make it a container???

My fault for unclear expression!  I mean: if it's an iterator, it's an
iterator.  All OTHER iterables (iterables that aren't iterators) are
(what some call) containers.

It's not QUITE that way, but Python would be easier to teach if
it were.

> > to Oren but he disliked it (because it meant readline would not
> > respect its numeric argument, if any, in that case).
>
> Hm, you should've sent it to me.  The numeric argument was a mistake I
> think.  Who ever uses it?

Not me, and I think it's advisory anyway according to the docs.

Still, it doesn't solve the reference-loop-between-two-deuced-things-
that-don't-cooperate-with-gc problem.  And I can't see how either
could be made into a WEAK reference given that xreadlines objects
in other contexts need to hold a strong ref to the file they work on --
we'd have to refactor xreadlines objects too, a core part holding a
weak ref and a shell around it (holding a strong ref to the file) to
support ordinary calls to xreadlines.xreadlines.  Messy:-(.


Alex