[Tutor] For Loop question

[Lie Ryan]

On Thu, Jun 26, 2008 at 3:18 AM, Dick Moores <rdm at rcblue.com> wrote:
> Hi I'm learning FOR loop now, very easy too learn. But I get confused
> to understand this code :
>
> myList = [1,2,3,4]
> for index in range(len(myList)):
>     myList[index] += 1
> print myList
>
> And the response is:
> [2, 3, 4, 5]
>
> Can you explain me as a newbie, how that code works ??


Ahhh... don't write it like that. It is not a pythonic way to use loop.

For-loop in python can loop over sequence (list, tuple, dictionary,
iterable, etc) directly (in Visual Basic, like For...Each loop), you
very rarely would need to use range/xrange for the iterator, and you
should never use len() to pass to range.

The loop would be much more simpler, and understandable this way:

myList = [1, 2, 3, 4]
outList = []
for x in myList:
    outList.append(x + 1)
print outList

or in a more elegant way, using list comprehension:

myList = [1, 2, 3, 4]
print [(x + 1) for x in myList]