Negative array indicies and slice()

[Andrew Robinson]

Ok, hopefully this is better.  I love my own e-mail editor...

I can see that the slice() function can pass in arbitrary arguments.
I'm not sure for lists, which is what the range is applied to, why an 
argument like "a" would be part of a slice.
I *really* don't see what the advantage of a slice class is over a mere 
list in the order of start, stop, step eg: [ 1,4,9 ]

In a dictionary, where "a" could be a key -- I wasn't aware that there 
was a defined order that the idea of slice could apply to.

When I look at the documentation,
http://www.python.org/doc//current/c-api/slice

The only thing that slice has which is special, is that the the length 
of the sequence can be given -- and the start and stop index are either 
trimmed or an error (exception???) is thrown.

Where is the information on the more general case of slice()? :-\

I am thinking, can one use the 'super' type of access, to override -- 
within the list object itself -- the __getitem__ method, and after 
pre-processing -- call the shadowed method with the modified 
parameters?  That would allow me to use the normal a[-4:6] notation, 
without having to write a wrapper class that must be explicitly called.

I'm thinking something like,

PyListObject.__getitem__= lambda self, slice: ....

--Andrew.