[Python-ideas] More useful slices (original) (raw)

Chris Angelico rosuav at gmail.com
Sun Feb 1 21:38:52 CET 2015

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

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