Sorting NaNs

[Steven D'Aprano]

On Sat, 02 Jun 2018 17:28:28 +0200, Peter J. Holzer wrote:

> On 2018-06-02 10:40:48 +0000, Steven D'Aprano wrote:
>> On Sat, 02 Jun 2018 09:32:05 +0200, Peter J. Holzer wrote:
>> > Also nope. It looks like NaNs just mess up sorting in an
>> > unpredictable way. Is this the intended behaviour or just an accident
>> > of implementation? (I think it's the latter: I can see how a sort
>> > algorithm which doesn't treat NaN specially would produce such
>> > results.)
>> 
>> 
>> Neither -- it is a deliberate decision
> 
> If it was a deliberate decicion I would say it was intentional.


As the author of the statistics module, I can absolutely and 
categorically tell you without even the tiniest doubt that the behavour 
of statistics.median with NANs is certainly not intentional.

The behaviour of median with NANs is unspecified. It is whatever the 
implementation happens to do. If it gives the right answer, great, and if 
it doesn't, it doesn't.

If somebody cares about this use case enough to suggest an alternative 
behaviour, I'm willing to consider it.



-- 
Steven D'Aprano
"Ever since I learned about confirmation bias, I've been seeing
it everywhere." -- Jon Ronson