[Tutor] Changing lists in place

[Bob Gailer]

Paul D. Kraus wrote:
> I have a list that I want to change in a for loop. It changes in the 
> loop but the changes are not persistant outside of the loop.
> I thought lists were mutuable objects 
They are.
> so I am a bit confused.
>
> Sample Code....
> #!/usr/bin/env python
> """ Testing lists """
>
> mylist = [ 'One    ', '   two', '   three   ' ]
> print mylist
> for element in mylist:
element is a variable to which the successive items in mylist are 
assigned. element has no "magic" connection to the list. 
>     element = element.strip()
In order to change a list item you must do something like:
mylist[itemIndex] = element.strip()

So you need both the item's value and its position in the list. That's 
what enumerate is for:

for itemIndex, element in enumerate(mylist):
    mylist[itemIndex] = element.strip()
>   [snip]