Reverse a string

reverse.py

"""
String reversal Algorithm

Technically we would do 'something'[::-1] to reverse a string but
as an excercise I did it myself without using additional memory.

This is technically a lie since strings are immutable in python but
it gives you the idea...

"""
from __future__ import print_function, unicode_literals

import math

if __name__ == "__main__":

    # string = u'mañana'
    string = 'superstar'
    print(string)

    string_chars = list(string)

    num_chars = len(string_chars)
    middle_char =  (num_chars - 1) / 2.0
    num_swaps = int(math.ceil(num_chars / 2.0))

    start_left = int(math.floor(middle_char))
    start_right = int(math.ceil(middle_char))

    for swap in range(0, num_swaps):
        left = start_left - swap
        right = start_right + swap
        string_chars[left], string_chars[right] = string_chars[right], string_chars[left]

    print(''.join(string_chars))