Extended slicing and Ellipsis - where are they used?

[Paddy]

On Sep 14, 1:50 am, James Stroud <jstr... at mbi.ucla.edu> wrote:
> Rodney Maxwell wrote:
> > The following are apparently legal Python syntactically:
> >    L[1:3, 8:10]
> >    L[1, ..., 5:-2]
>
> > But they don't seem to work on lists:
> >>>> l = [0,1,2,3]
> >>>> l[0:2,3]
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > TypeError: list indices must be integers
> >>>> l[...]
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > TypeError: list indices must be integers
>
> > So where is this extended slicing used?
>
> AFAICT this syntax is not used in the standard library. However, the
> mega-beauty of it is that you can make use of it in your own classes:
>
> py> class Bob(list):
> ...   def __getitem__(self, i):
> ...     try:
> ...       return [list.__getitem__(self, j) for j in i]
> ...     except TypeError:
> ...       return list.__getitem__(self, i)
> ...
> py> b = Bob(xrange(15, 30))
> py> b[3, 5, 7, 13]
> [18, 20, 22, 28]
>
> James

And the ellipses ... ?

- Paddy.