This is what I currently have: wordlist = [fox, aced, definite, ace] for word in wordlist: a = len(word) if (ord(word[a-(a-1)] - ord(word[(a-a)])) == ord(word[a-(a-2)])-ord(word[a-(a-1)]: print "success", word else: print "fail", word What I'm trying to do is calculate the ASCII values between each of the letters in the word. And check to see if the ord of the letters are increasing by the same value. so for fox, it would check if the difference between the ord of 2nd and 1st letters are equal to the ord difference of the 3rd and 2nd letters. However, with my current 'if' statement, only the first 3 letters of a word are compared. How can I rewrite this statement to cover every letter in a word of length greater than 3? Sorry if I can't present this clearly, thanks for your time.