Password Guesser Project

[RedSkeleton007]

I now get the error:

#while guess[len(guess)-1] <= AlphaNum[len(AlphaNum)-1]:
#IndexError: string index out of range

If I'm not mistaking, I looks like my program is trying to compare a one-char length guess string with a three-char length AlphaNum (such as 'a' with 'abc'). But that's not what what I'm trying to do. Currently, my guess string is only one char as I have declared it on line 9 of the code below, so guess[len(guess)-1] should just equal guess[0], and AlphaNum[len(AlphaNum)-1] should simply be referring to the last char in AlphaNum:

#!/usr/bin/env python3
#PasswordGuesser.py

AlphaNum = "abc"
guess = ""
guessMatches = False
password = "b"
guessLength = len(guess)
guessLength = 1 #start with a guess length of just one char

def iterateAlphaNum():
    i = 0
    while i < len(AlphaNum):
        guess[0] == AlphaNum[i]
        i += 1


#Master While Loop: while the last char of the guess string has not yet passed
#the last char in AlphaNum
while guess[len(guess)-1] <= AlphaNum[len(AlphaNum)-1]:
    guess[0] = iterateAlphaNum()
    print(guess)
    if guess == password:
        guessMatches = True
        print()
        print("Found the password! It's " + str(guess))
        break

Any ideas?