Help doing it the "python way"

[Emile van Sebille]

On 5/24/2012 2:30 PM Paul Rubin said...
> Paul Rubin<no.email at nospam.invalid>  writes:
>>      new_list = chain( ((x,y-1), (x,y+1)) for x,y in coord_list )
>
> Sorry:
>
>     new_list = list(chain( ((x,y-1), (x,y+1)) for x,y in coord_list))


 >>> from itertools import chain
 >>> coord_list = zip(range(20,30),range(30,40))
 >>> a = [((x,y-1),(x,y+1)) for x,y in coord_list]
 >>> b = list(chain(((x,y-1),(x,y+1)) for x,y in coord_list))
 >>> a == b
True
 >>>

So, why use chain?  Is it a premature optimization?  Similar to the 
practice of using "".join(targets) vs targeta+targetb+...+targetn?

Emile