I am at the "write a function that reverses a string without creating a new string" question and this is the answer on the site:

  def reverse(str):
    left_ptr = 0
    right_ptr = len(str) - 1
    middle = len(str) / 2
    while left_ptr <= middle:
        # swap
        temp = str[left_ptr]
        str[left_ptr] = str[right_ptr]
        str[right_ptr]= temp

wouldn't this create an infinite loop? You're never incrementing / decrementing left_ptr or right_ptr.

Not to mention, strings are immutable in Python.

You can't even assign by index with strings

str[0] = ... will trigger an exception

I see that and want to do it by appending backwards off the end of the string, then move the pointer to the new beginning. Is that "creating a new string"? Or just making a poopy on the floor for the garbage collector?

"Double the length of the old string and then cut it in half" isn't against the rules, right?

I don't know if it is against the rules, my approach was a recursive function.

I would answer :

    def reverse(str):
        return str[::-1]

Am I missing the point ?

That creates a new string (the one returned) :)

Thats what I would do. Then again, I always get rejected when I do these type of interviews...

    def reverse(string='abc123'):
        for pos in xrange(-len(string)+1, 1):
            string += string[abs(pos)]

        return string[len(string)/2:]

Fair?

Woops--yeah, that's pretty bad. Somehow this one made it through testing. Fixing!

Yup.