Walking lists

[Tim Chase]

lallous wrote:
> L = (
>   (1, 2, 3),
>   (4,),
>   (5,),
>   (6, 7)
> )
> 
> What I want, is to write the for loop, something like this:
> 
> for (first_element, the_rest) in L:
>   print first_element
>   for x in the_rest:
>     # now access the rest of the elements

Python 3 introduced a variable tuple assignment which I 
suspect[*] would work in this context:

   for first, *rest in L: # note the asterisk
     print first
     for x in rest:
       do_stuff(x)

> I know I can :
> for x in L:
>     first = x[0]
>     rest = x[1:]

However in 2.x, this is the way to do it.  Though if you want to 
abstract the logic, you can move it to a generator:

   def splitter(i):
     for t in i:
       yield t[0], t[1:]

   for first, rest in splitter(L):
     print first
     for x in rest:
       do_stuff(x)

-tkc



[*] not having py3 on this machine, I can't readily verify this.