My version of the 13 characters per line problem described here: http://blog.8thlight.com/uncle-bob/2012/04/20/Why-Is-Estimating-So-Hard.html (estimated 10 minutes, took me 30)

word_wrap.py

the_str = """Four score and seven years ago our fathers brought forth upon this \
continent a new nation, conceived in liberty and dedicated to the \
proposition that all men are created equal..."""

def word_wrap(the_str, chars_per_line):
    '''
    Returns formatted string based on number of characters per line
    '''
    iterator,space_pos,line_count = 0,0,0
    output = the_str
    # Go through the string's characters one at a time
    while iterator < len(output):
        # If we come across a space, we'll note where
        if output[iterator] == ' ':
            space_pos = iterator
        # Once we get to the end of the line, we need to work out where to put the line break
        if line_count == (chars_per_line-1):
            # If we have found a space since the last line break insert
            # then break the string in half at the space and put the break there
            if space_pos > iterator-(chars_per_line-1):
                output = output[:space_pos] + ' \n' + output[space_pos+1:]
                # We're going to put our iterator back where the space was, plus one more
                # to get in front of the line break
                iterator = space_pos+1
            # If we haven't found a space, then we'll just push it in the middle
            # of the word, adding a hyphen
            else:
                output = output[:iterator] + '-\n' + output[iterator+1:]
            # We're now working on a new line, start the counter again
            line_count = 0
        iterator += 1
        line_count += 1

    return output

if __name__ == '__main__':
    print word_wrap(the_str, 13)