[Python-ideas] Fast sum() for non-numbers

[Steven D'Aprano]

On 06/07/13 06:25, Terry Reedy wrote:

> When Alex said that it was not possible to determine if the start value is a number, he was talking in the context of old style classes where the type of every user class was 'Class' and the type of every user instance was 'Instance' (or something like that). In Python 3, with ABCs, isinstance(start, Number) would solve the problem as long as the requirement were documented.


For the record, it has always been possible to check if something is a number:


try:
     x + 0
except TypeError:
     print "x is not a number"



-- 
Steven