PEP-308 a "simplicity-first" alternative

[holger krekel]

Peter Hansen wrote:
> Paul Rubin wrote:
> [on YATOP] 
> > In fact it's not even obvious what it does.  
> > What should the value of (2 and 0 else 3) be?
> 
> Hmm... (2 and 0) gives the value 0, so the result should clearly
> be whatever (0 else 3) returns, which logically should be 3, right?
> 
> (In other words, I agree.  If you know it's a ternary op, you can
> figure it out.  If you don't, it's entirely non-obvious what it's
> doing, and reads to me more like a latent syntax error than anything
> else.)

Every ternary op construct needs time to get used to it, i am afraid. 
To me 'else' doesn't hint at a boolean operator like 'or' but 

    a) that there is a "not-else" part before it 

    b) that there is an alternative part after it 

Everything else would be surprising. From there it's only a short 
way to "getting it".  In real life examples (taken from stdlib) like

    run==1 and '' else 's'

    cl and cl.__name__ else ''

    unicode and self.ugettext else self.gettext

i don't think it's "entirely non-obvious" for you anymore? 
Sure, it has to be taught to newcomers but only as an "addon"
to boolean expressions and as a rather minor thing. no big deal.

Admitted, it's a bit odd but many of us find seeing 'if' and 
'else' (and whatnot) in expressions odd, too.  It might not be 
100% satisfying but then it is a rather simple change which 
fixes one particular problem avoiding to invent 
another kind of expression.

Also it's nice that if you discover you don't need an else-part 
anymore you can just delete it.  With the other proposals you have 
to rewrite your expression - using another idiom.  

regards,

    holger