cipher.py

def encode(char, shift, operation):
    if char.isdigit():
        offset = ord(char) - ord('0')
        if operation == "encode":
            shifted = (offset + shift) % 10
        elif operation == "decode":
            shifted = (offset - shift) % 10
        else:
            raise ValueError("Invalid Operation!")
        return chr(ord('0') + shifted)

    elif char.isalpha():
        base = ord('A') if char.isupper() else ord('a')
        offset = ord(char) - base
        if operation == "encode":
            shifted = (offset + shift) % 26
        elif operation == "decode":
            shifted = (offset - shift) % 26
        else:
            raise ValueError("Invalid Operation!")
        return chr(base + shifted)
    else:
        return char

def encodeOrDecodeString(stringToProcess, shift, operation):
    newString = ""
    for x in range(0, len(stringToProcess)):
        processedChar = encode(stringToProcess[x], shift, operation)
        newString += processedChar
    return newString


def main():
    operation = str(input("Encode or Decode: "))
    
    assert operation.lower() == "encode" or operation.lower() == "decode", "Invalid operation!"


    stringToProcess = str(input("Enter String: "))
    shift = input("Enter shift number: ")
    assert shift.isdigit(), NaN

    print(encodeOrDecodeString(stringToProcess, shift, operation))
    



if __name__ == "__main__":
    main()