So need to check if a string's characters are ascending alphabetically and if that ascent is evenly spaced. a = "abc" b = "ceg" So a is alphabetically ascending and it's spacing is 1 (if you convert to the ordinal values they are 97,98,99). And b is also alphabetically ascending and it's spacing is 2 (99,101,103). And I am sticking with the following code: a = 'jubjub' words1 = [] ords = [ord(letter) for letter in a] diff = ords[1] - ords[0] for ord_val in range(1, len(ords)-1): if diff > 0: if ords[ord_val + 1] - ords[ord_val] == diff: if a not in words1: words1.append((a, diff)) print words1 How come 'jubjub' works, 'ace' works, but 'catcat' doesn't?