Intermediate Python

We have added some code to the beginning of morse.encode to check, in the case of the passed string being an English string, that it contains no !. If it does, we raise a ValueError.

From the docs:

ValueError: Raised when an operation or function receives an argument that has the right type but an inappropriate value, and the situation is not described by a more precise exception such as IndexError.

letter_to_morse = {
    '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':'--..',
    '0':'-----', '1':'.----', '2':'..---', '3':'...--', '4':'....-',
    '5':'.....', '6':'-....', '7':'--...', '8':'---..', '9':'----.', ' ':'/'
}


def encode(message):
    if "!" in message:                                            # ← new code
        raise ValueError(f"'!' is not valid in English strings")  # ←
    
    morse = []

    for letter in message:
        letter = letter.lower()
        morse_letter = letter_to_morse[letter]
        morse.append(morse_letter)

    morse_message = " ".join(morse)
    
    return morse_message


# We need to invert the dictionary. This will create a dictionary
# that can go from the morse back to the letter
morse_to_letter = {}
for letter in letter_to_morse:
    morse = letter_to_morse[letter]
    morse_to_letter[morse] = letter


def decode(message):
    english = []

    morse_letters = message.split(" ")

    for letter in morse_letters:
        english_letter = morse_to_letter[letter]
        english.append(english_letter)

    english_message = "".join(english)
    
    return english_message