[Python-ideas] More useful slices

[Chris Barker - NOAA Federal]

Please go read PEP 204, as Nick suggested. It would be nice if there was
more Kongo as to why it was rejected, but it was, indeed, rejected.

I also recall a lot of drawn out threads about more compact syntax for a
for loop over integers, such as making the integer object iterable:

for I in 10:
    pass

Which were also all rejected.

Unless someone comes up with a compelling argument that something has
changed, it seems this conversation has been had already.

-Chris



On Feb 2, 2015, at 7:02 AM, Neil Girdhar <mistersheik at gmail.com> wrote:

But it is meaningful to have a range with an unspecified stop.  That's
itertools.count.

On Sunday, February 1, 2015 at 12:27:53 PM UTC-5, Steven D'Aprano wrote:
>
> On Sun, Feb 01, 2015 at 04:13:32PM +0100, Todd wrote:
> > Although slices and ranges are used for different things and implemented
> > differently, conceptually they are similar: they define an integer
> sequence
> > with a start, stop, and step size.
>
> I'm afraid that you are mistaken. Slices do not necessarily define
> integer sequences. They are completely arbitrary, and it is up to the
> object being sliced to interpret what is or isn't valid and what the
> slice means.
>
> py> class K(object):
> ...     def __getitem__(self, i):
> ...             print(i)
> ...
> py> K()["abc":(2,3,4):{}]
> slice('abc', (2, 3, 4), {})
>
>
> In addition, the "stop" argument to a slice may be unspecified until
> it it applied to a specific sequence, while range always requires
> stop to be defined.
>
> py> s = slice(1, None, 2)
> py> "abcde"[s]
> 'bd'
> py> "abcdefghi"[s]
> 'bdfh'
>
> It isn't meaningful to define a range with an unspecified stop, but it
> is meaningful to do so for slices.
>
>
> In other words, the similarity between slices and ranges is not as close
> as you think.
>
>
> --
> Steven
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