[Python-Dev] non-integer arguments to simple slices in 1.6?

[Guido van Rossum]

> We have a problem here, but I think it's in the fact that 
> currently certain slices end up in __getitem__ and some in 
> __getslice__.
> 
> IOW, I think that __getitem__ should return an item, and this 
> fix (while clever) just compounds a mistake.

Agreed in an ideal world, but it's done like this for backwards
compatibility.

The proper solution would be for __getslice__ to always get the raw
values given to the slice, but so that __getslice__ takes an optional
third argument which gets the 3rd slice value if present.  So x[i:j]
results in x.__getslice__(i,j) while x[i:j:k] results in
x.__getslice__(i,j,k).  Missing values are replaced with None, so that
x[:] results in x.__getslice__(None, None) and x[::] in
x.__getslice__(None, None, None).

This is pretty backwards incompatible!

Perhaps to the devil with b/w compat?

Note that C extensions also get too much service for slicing.

It seems a somewhat tedious project to clean all of this up...

--Guido van Rossum (home page: http://dinsdale.python.org/~guido/)