Coding a message with % 26 tactics (Codewars)

# Global variable
alphabet = "abcdefghijklmnopqrstuvwxyz"

# **********************************************************************************************************************
# **********************************************************************************************************************
# MY FUNCTION
def code(message, num):

    # 1. I create the map/directory: 'a' --> 1, 'b' ---> 2, ....
    counter = 0
    directory = {}
    for ch in alphabet:
        counter += 1
        directory[ch] = counter
    # print(directory)

    # 2. Using this map/directory, I will convert the message into a sequence of numbers
    sequence = []                            # List og integer numbers
    for ch in message:
        # For every character "ch" in the string "message": I will scan all the directory to find matching characters
        for key, value in directory.items():
            if ch.lower() == key:
                sequence.append(value)
    # print(sequence)

    # 3. I will alter the elements of the sequence based on the following rule:
    # If sequence[i] = x, then the new value will be: (x * num) % 26
    # Like a function:      f(x): x ---> (x * num) % 26
    for i in range(0, len(sequence)):
        sequence[i] = (sequence[i] * num) % len(alphabet)

    # print(sequence)

    # 4. Then, having the numbers in the list "sequence", I match them with the appropriate characters of the alphabet
    codedMessage = ""
    for i in range(0, len(sequence)):
        # For every number in my list, I will scan all the directory: And when the number is equal to a value of a directory, I do the following
        for key, value in directory.items():
            if sequence[i] == value:
                codedMessage += key

    return codedMessage


# **********************************************************************************************************************
# **********************************************************************************************************************
# MAIN FUNCTION
print()
print("Give me a message and then a number to cipher the given message. Be careful! It must contain only lowercase letters!")
print("If you contain any numbers or special characters in the string/message, they will be ignored...")
message = input("Message: ")
number = int(input("Number: "))
codedMessage = code(message, number)
print("Coded Message: " + codedMessage)