faster than list.extend()

[Tim Chase]

Hyunchul Kim wrote:
> Hi, all.
> 
> I want to improve speed of following simple function.
> Any suggestion?
> 
> **********
> def triple(inputlist):
>   results = []
>   for x in inputlist:
>     results.extend([x,x,x])
>   return results
> **********

Several ways occur to me:

   def t1(i):
     for x in i:
       yield x
       yield x
       yield x

   def t2(i):
     r = range(3)
     return (x for x in i for _ in r)


I prefer to return generators in case the input is large, but in 
both cases, you can just wrap it in list() like

   list(t1(inputlist))

or in t2(), you can just change it to use

     return [x for x in i for _ in r]

-tkc