def LetterChanges(str): 

  alpha = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y']
  capital = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y']
  vowel = ['a', 'e', 'i', 'o', 'u', ]
  word = str.split()
  for i in range(len(word)):
    if word[i] == 'z':
      word[i] = 'a'
    else:
      word[i] = alpha[alpha.index(word[i]) + 1]
    if word[i] in vowel:
      word[i] = capital[alpha.index(word[i])]
      
  answer = word.join()
  return answer
      
# keep this function call here  
# to see how to enter arguments in Python scroll down
print LetterChanges(raw_input())

 => python
Python 2.7.6 (default, Jan 28 2014, 15:43:10)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> str = "someword"
>>> str.split()
['someword']
>>> list(str)
['s', 'o', 'm', 'e', 'w', 'o', 'r', 'd']
>>>

>>> word = 'word'
>>> for letter in word:
...     print(letter)
... 
w
o
r
d
>>>

def LetterChanges(str): 

ref = "abcdefghijklmnopqrstuvwyz"
vowel = "aeiou"
str2 = ""
    for i in range(len(str)):
        if str[i] == "z":
          str2 = str2 + "a"

def LetterChanges(str): 
  ret = ''
  for ch in str:
    if ch.isalpha():
      ch = chr(ord('a') + (ord(ch) + 1 - ord('a')) % 26)
    if ch in 'aeiou':
      ch = ch.upper()
    ret += ch
  return ret

>>> chr(ord('a') - 32)
'A'

import string

def silly_function(word):
    s = string.ascii_lowercase
    ans = ''
    v = 'aeiou' ## and sometimes 'y' and 'w', obv.

    for letter in word:
        t = s[s.index(letter) - (len(s) - 1)]
        if t in v:
            t = t.upper()
        ans += t
    return ans

print(silly_function('xyz'))

t = s[s.index(letter) - (len(s) - 1)]