Pre-PEP: reverse iteration methods

[Andrew Dalke]

John Roth:
> There are objects that support iteration that
> don't support len(), such as file objects.

Sure.  Then it'll given an exception.  The implementation
should turn around and raise the proper exception there
instead of a "len doesn't exist" one.

There's also a problem that len works on a dict but
__getitem__(int) will only work if the dict stores 0->n-1
as keys.

> This has got the advantage, of course, that it would
> automatically work on all objects that support
> an sequence-like protocol, though.

Yup.

> Frankly, I prefer the notion of a method.

While I don't.  There are many, many ways to
iterate through a list.  (What about all evens
followed by all odds?)  Right now they are all
done by using a function which creates an iterator
across a container.  If it's a method then you've
said that reverse_iter is special enough that it
must be a method, which seems strange for something
which is so infrequently used.

                    Andrew
                    dalke at dalkescientific.com