[Python-Dev] Rationale for sum()'s design?

[Eric Nieuwland]

Guido van Rossum wrote:
> I think the conclusion should be that sum() is sufficiently
> constrained by backwards compatibility to make "fixing" it impossible
> before 3.0. But in 3.0 I'd like to fix it so that the 2nd argument is
> only used for empty lists.

Which is not unlike the get() method of dicts. So may be the default 
should be None?