returning True, False or None

[Mick Krippendorf]

Fredrik Lundh wrote:
> Steven Bethard wrote:
>> Raymond Hettinger wrote:
>>> 
>>> return max(lst)
>> 
>> Very clever!  Thanks!
> 
> too clever.  boolean > None isn't guaranteed by the language
> specification: 
> 
>     http://docs.python.org/ref/comparisons.html
> 
>     "... objects of different types always compare unequal, and are
>     ordered consistently but arbitrarily. /.../ In the future, the
>     comparison rules for objects of different types are likely to
>     change. ..." 

Then maybe like this:

 >>> def max_of_two_with_None_less_than_any_other_object(e1, e2):
 ...     if e1 == None:
 ...         return e2
 ...     elif e2 == None:
 ...         return e1
 ...     else:
 ...         return max(e1, e2)

 >>> reduce(max_of_two_with_None_less_than_any_other_object, lst)

Mick.