caesar.py

def caesar_cipher(_str, shift):
    alphabet = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
    numbers = [str(x) for x in range(10)]   # creates an array of numbers 0-9
    _str = list(_str.lower())   # makes input string a list

    for i in range(len(_str)):
        if _str[i] in alphabet:
            helper(alphabet, i, shift, _str)
        elif _str[i] in numbers:
            helper(numbers, i, shift, _str)

    return ''.join(_str)

def helper(arr, i, shift, _arr):
    index = arr.index(_arr[i])
    while index+shift > len(arr)-1:
        shift -= len(arr)
    while index+shift < 0:
        shift += len(arr)
    _arr[i] = arr[index+shift]