newbie question

[Gary Herron]

On 04/01/2011 12:52 PM, Karl wrote:
>
> Hello,
>
>
> one beginner question:
>
>
> aList = [0, 1, 2, 3, 4]
>
> bList = [2*i for i in aList]
>
> sum = 0
>
> for j in bList:
>
> sum = sum + bList[j]
>

Your j is already an element of bList.  You don't need to index bList 
again.  Instead do
     for b in bList:
             sum = sum+b

> print j
>
>
> 0
>
> 2
>
> 4
>
> *IndexError:* 'list index out of range'
>
> Why is j in the second run 2 and not 1 in the for-loop?? I think j is 
> a control variable with 0, 1, 2, 3, ...
>
No, it's not a control variable, it's the actual elements of the list.


If you want a control variable as an index you can do
   for j in range(len(bList)):
         sum = sum + bList[j]

But that is less efficient


>
> Thanks!
>
>
> Karl
>

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