[Python-Dev] list comprehensions again...

Gordon McMillan gmcm@hypernet.com
Tue, 11 Jul 2000 17:47:56 -0400

Barry A. Warsaw wrote:

> Sorry, but I'm being to think that both the list comprehensions
> and parallel for loops are looking pretty dodgy. 

I'm with Barry here (despite the public humiliation the 
association involves).

My expectations (from examples) correlates to accompanying 
explanations no better than random choice. I *thought* I liked 
Greg Ewing's original proposal, but at this point I see 
syntactic salts of ammonia around one very clear idiom 
(nested fors) and one less intuitive but unambiguous idiom 

I like the set notation, but there's a big impedance mismatch 
to Python. I'd be tempted to spell "cartesian product" as a 

To put it another way:
 - syntactic sugar for nested "for" loops would be nice, but 
there's no crying need for it
 - the current spelling of parallel loops is awkward and 
probably does warrant syntactic sugar (despite Greg Wilson's 
experiment that it's not what's expected).

If list comprehensions are going to do *both*, the difference in 
how they're spelled will have to be obvious and intuitive, or we 
might as well just keep explaining how to use map.

- Gordon