[Python-ideas] More useful slices

[Chris Angelico]

On Mon, Feb 2, 2015 at 5:13 AM, Thomas Kluyver <thomas at kluyver.me.uk> wrote:
> Iterating over a slice object would work like you were lazily taking that
> slice from itertools.count() - i.e. iter(a:b:c) would be equivalent to
> islice(count(), a, b, c). This would also mean that (3:) would have a
> logical meaning without having to modify range objects to support an
> optional upper bound. I don't see any logical way to iterate over a slice
> defined with negative numbers (e.g. (-4:)), so presumably iter(-4:) would
> raise an exception.

If you're going to start defining things in terms of
itertools.count(), I'd prefer to first permit a range object to have
an infinite upper bound, and then define everything in terms of a
sliced range - range objects already support clean slicing.

Is there any particular reason for range objects to disallow infinite
bounds, or is it just that nobody's needed it?

ChrisA