Caesar Cipher

caesar.py

def caesar(plainText, shift):
    """Caesar Cipher implementation.
       Upper and lower case letters are kept accordingly, non-alphabetic characters are ignored.
       Implementation taken from here: https://stackoverflow.com/q/8886947/1245214
       
       :param plainText: the text to be ciphered
       :param shift: shift value for the cipher
       :return: the ciphered text
    """
    cipherText = ""

    for ch in plainText:
        finalLetter = ch
        if ch.isalpha(): 
            finalLetter = chr((ord(ch.lower()) - 97 + shift) % 26 + 97)        
        if ch.isupper():
            finalLetter = finalLetter.upper()

        cipherText += finalLetter

    return cipherText