Python 3.0 - is this true?

[Robin Becker]

M.-A. Lemburg wrote:
> On 2008-11-11 02:10, Steven D'Aprano wrote:
>> On Mon, 10 Nov 2008 12:51:51 +0000, Duncan Grisby wrote:
>>
>>> I have an object database written in Python. It, like Python, is
>>> dynamically typed. It heavily relies on being able to sort lists where
>>> some of the members are None. To some extent, it also sorts lists of
>>> other mixed types. It will be very hard to migrate this aspect of it to
>>> Python 3.
>> No, it is "very hard" to sort *arbitrary* objects consistently. If it 
>> appears to work in Python 2.x that's because you've been lucky to never 
>> need to sort objects that cause it to break. 
> 
> If you read Duncan's email, he isn't talking about arbitrary objects
> at all. He's just referring to being able to sort lists that contain
> None elements.
> 
> That's far from arbitrary and does work consistently in Python 2.x -
> simply because None is a singleton which is special cased in Python:
> None compares smaller to any other object in Python.
> 
> I'm not sure why this special case was dropped in Python 3.0. None
> is generally used to be a place holder for a n/a-value and as
> such will pop up in lists on a regular basis.
> 
> I think the special case for None should be readded to Python 3.0.
> 
I agree here, it seems strange that cmp(None,None) is exceptional. Clearly the 
is relation applies to None so does ==. Do we not have a sorting order for sets 
with one element? My maths is now shot, but I seem to remember there are 
automatic orders for such simple sets.
-- 
Robin Becker