[Python-Dev] default of returning None hurts performance?

[Xavier Morel]

On 1 Sep 2009, at 02:01 , Greg Ewing wrote:
> I don't think the unpredictability that would introduce
> would be a good idea.
I fail to grasp the unpredictability of "the last expression evaluated  
in the body of a function is its return value".

It couldn't work in Python because statements aren't expressions,  
therefore I think

     def foo():
         if cond:
             3
         else:
             4

would break (given if:else: doesn't return a value, the function  
couldn't have a return value), but in languages where everything is an  
expression (where if:else: does return a value) there's nothing  
unpredictable about it.