[Python-ideas] More useful slices

[Todd]

On Mon, Feb 2, 2015 at 1:48 PM, Paul Moore <p.f.moore at gmail.com> wrote:

> On 2 February 2015 at 10:22, Todd <toddrjen at gmail.com> wrote:
> > Let's just call this a range literal.  It has some features similar to
> > slices, but not all.
>
> So what would d[1:10:2] mean? d[Slice(1,10,2)] or d[range(1,10,2)]?
>
> At the moment 1:10:2 is a slice literal, and you're proposing to
> repurpose it as a range literal? What have I missed? Because that's
> never going to satisfy backward compatibility requirements.
>
>
No, I am proposing that (x:y:x) is syntactic sugar for range(x, y, z).
Note the parentheses.  Currently wrapping slice notation in a parentheses
is not valid syntax, so there is no backwards-compatibility issues.  Bare
slice notation, without the parentheses or in an index, will remain invalid
syntax.

I am absolutely *not* proposing that anything change with existing slices.
d[1:10:2] would not change at all.  d[(1:10:2)] would become valid syntax,
but it is not the use-case that prompted it and I doubt anyone would
actually want to do that.

I am more interested in something like:

for i in (1:10:2):
   pass

I am also *not* proposed the following syntax, since it would be ambiguous
in many cases:

for i in 1:10:2:
   pass
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