[Tutor] For loop breaking string methods

[bob gailer]

On 4/26/2010 3:38 PM, C M Caine wrote:
> Why does this not work:

By "work" you mean "do what I want it to do".

> >>> L = [' foo ','bar ']
> >>> for i in L:
>     i = i.strip()

This creates a new local variable named i. It does not affect L. This 
has nothing to do with loops nor is it strange behavior - it is expected 
behavior.

Consider the loopless equivalent:

 >>> i = L[0]
 >>> i = i.strip()
 >>> L
[' foo ', 'bar ']

>
>
> >>> L
> [' foo ', 'bar ']
> >>> # note the leading whitespace that has not been removed.
>
> But this does:
> >>> L = [i.strip() for i in L]
> >>> L
> ['foo', 'bar']
>
> What other strange behaviour should I expect from for loops?
>

None - loops do not have "strange" behaviors.
Perhaps "unexpected" but that is a result of not understanding an aspect 
of the language.

-- 
Bob Gailer
919-636-4239
Chapel Hill NC