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#!/usr/bin/python

from string import join
import re

def reverse_string(s):
    """ Does a simple character-based reverse of a string.

        This could alternatively be done by calling reverse_chars below,
        but it showcases a different method of reversing the string.  """
    splitter = re.compile(r'\s')

    list = splitter.split(s)
    space = ' '
    list.reverse()
    
    out = join(list, ' ')
    return out


def reverse_chars(s, l):
    """ Reverse the first l characters of string s. """
    p1 = 0
    p2 = l - 1
    while p1 != p2:
        t = s[p1]
        s[p1] = s[p2]
        s[p2] = t
        p1 = p1 + 1
        p2 = p2 - 1
        
        
def reverse_string_in_place(s):
    """ 'Clever' algorithm for reversing a string in place.
    
    Step 1:  Reverse the string, character by character.
    Step 2:  Reverse each word
    """
    

    reverse_chars(s, len(s))
    
    c = 0
    while c < len(s):
        p1 = c
        p2 = c
        while s[p2] != " " and p2 < len(s):
            p2 = p2 + 1
            reverse_chars(p1, p2)
            c = p2 + 1
            
        


            
s = "These are words in a string"
print reverse_string(s)