exercise 8.12 - rotate_word

"""=======================

exercise 8.12

======================"""

def rotate_word (word, num_shift):

    new_letter = ""

    new_word = ""

    word_lower = word.lower()

    

    for letter in word_lower:

        #rotate letter

        new_ltr_position = ord(letter)+num_shift

        

        # rotate z-->a or z<--a

        if new_ltr_position < ord('a'): #rotate z<--a

            new_ltr_position = new_ltr_position + 26

        elif new_ltr_position > ord('z'): #rotate z-->a

            new_ltr_position = new_ltr_position - 26

        

        #build new word

        new_letter = chr(new_ltr_position)

        new_word = new_word + new_letter

    return new_word

    

print rotate_word("melon",-10)

print rotate_word("cheer",7)