Increments a string. For example, aaab would return aaac, abcd would return abce, abzz would return aczz, and zzzz would return zzzz

increment_string.py

from string import ascii_lowercase


def increment(string):
    """
    Increments a string alphabetically
    increment("aabc") would return "aabd"
    :param text: Just some plain english text
    :return: Incremented string
    """
    # Splits the string into a list of lowercase characters
    string = list(string.lower())

    # Loops over the list of character and when it finds a character that isn't z
    # It increments that character a -> b or d -> e
    idx = -1
    for letter in reversed(string):
        if letter != 'z':
            string[idx] = ascii_lowercase[ascii_lowercase.index(letter) + 1]
            # Stops the loop so it does not increment every letter in the string
            break
        # Index variable is required because otherwise it would be (1, 2, 3, 4, etc...)
        idx -= 1
        continue
    return ''.join(string)