Code:

#!/usr/bin/python

def main():
   # declaraing the variable and initializing to their default values
   word=""
   vowels = 'aeiou'
   v_index = -1
   flag = 1

   # running an infinite loop
   while(flag):
       # Taking word as input from user
       word = raw_input("Enter a word: ")
       # computing length of the word and converting word to lower case
       w_len = len(word)
       word = word.lower()
       # if the word entered is 'quit' it will quit out from the loop and program terminates
       if word == 'quit':
           break
       # iterating through each letter in word to find the first position of vowel
       for i, ch in enumerate(word):
           if ch in vowels:
               v_index = i
               break
       # if v_index != -1 that means given word has a vowel
       if v_index != -1:
           # if v_index is 0 that means vowel is at first position in the word
           if v_index == 0:
               print word + 'way'
           # if v_index is > 0 that means vowel is not at first position but somewhere in the middle or last
           elif v_index > 0:
               print word[v_index:w_len] + word[0:v_index] + 'ay'


if __name__=='__main__':
   main()


Execution and output:
186590cb0725:Python bonkv$ python pig_latin.py
Enter a word: dog
ogday
Enter a word: scratch
atchscray
Enter a word: is
isway
Enter a word: apple
appleway
Enter a word: Hello
ellohay
Enter a word: a
away
Enter a word: quit
186590cb0725:Python bonkv$ python pig_latin.py
Enter a word: bat
atbay
Enter a word: QUIT
186590cb0725:Python bonkv$ python pig_latin.py
Enter a word: ball
allbay
Enter a word: Quit