Looping around a simple list of tuples

[Andrew Bennetts]

On Sun, Apr 27, 2003 at 04:45:16AM +0000, Martin d'Anjou wrote:
> I have a list of tuples, each tuple is a (scalar , list)
> 
> a=[("r1",[1,2,3]),("r2",[8,9,10]),("r5",[12,14,16])]
> 
> for el in a:
>    print el
>    for r,l in el:
>       print "R "+`r`
>       print "L "+`l`
> 
> ('r1', [1, 2, 3])
> R 'r'
> L '1'
> Traceback (innermost last):
>   File "<stdin>", line 3, in ?
> ValueError: unpack list of wrong size
> 
> In my mind, the 'el' implicit variable is a tuple, and the for r,l loop 
> should just work but it does not. How come?

I think what you want is simply:

    for r,l in a:
        print "R "+`r`
        print "L "+`l`

Which could be spelt out as:

    for el in a:
        r, l = el
        print "R "+`r`
        print "L "+`l`

Does this make sense?
    
-Andrew.