[Python-Dev] PEP for adding an sq_index slot so that any object, a or b, can be used in X[a:b] notation

Nick Coghlan ncoghlan at gmail.com
Tue Feb 14 13:08:47 CET 2006

Guido van Rossum wrote:
> On 2/10/06, Mark Russell <mrussell at verio.net> wrote:
>> On 10 Feb 2006, at 12:45, Nick Coghlan wrote:
>> An alternative would be to call it "__discrete__", as that is the key
>> characteristic of an indexing type - it consists of a sequence of discrete
>> values that can be isomorphically mapped to the integers.
>> Another alternative: __as_ordinal__.  Wikipedia describes ordinals as
>> "numbers used to denote the position in an ordered sequence" which seems a
>> pretty precise description of the intended result.  The "as_" prefix also
>> captures the idea that this should be a lossless conversion.
> Aren't ordinals generally assumed to be non-negative? The numbers used
> as slice or sequence indices can be negative!

The other problem with 'ordinal' as a name is that the term already has a 
meaning in Python (what else would 'ord' be short for?).

I liked index from the start, but I thought we should put at least a bit of 
effort into seeing if we could come up with anything better. I don't really 
see any way that either 'discrete' or 'ordinal' can be said to qualify as 
better :)


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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