Function __prepare

ciphers/trifid_cipher.py:62–121

A helper function that generates the triagrams and assigns each letter of the alphabet to its corresponding triagram and stores this in a dictionary (`character_to_number` and `number_to_character`) after confirming if the alphabet's length is ``27``. >>> test = __prepare

(
    message: str, alphabet: str
)

def __prepare(
    message: str, alphabet: str
) -> tuple[str, str, dict[str, str], dict[str, str]]:
    """
    A helper function that generates the triagrams and assigns each letter of the
    alphabet to its corresponding triagram and stores this in a dictionary
    (`character_to_number` and `number_to_character`) after confirming if the
    alphabet's length is ``27``.

    >>> test = __prepare('I aM a BOy','abCdeFghijkLmnopqrStuVwxYZ+')
    >>> expected = ('IAMABOY','ABCDEFGHIJKLMNOPQRSTUVWXYZ+',
    ... TEST_CHARACTER_TO_NUMBER, TEST_NUMBER_TO_CHARACTER)
    >>> test == expected
    True

    Testing with incomplete alphabet

    >>> __prepare('I aM a BOy','abCdeFghijkLmnopqrStuVw')
    Traceback (most recent call last):
        ...
    KeyError: 'Length of alphabet has to be 27.'

    Testing with extra long alphabets

    >>> __prepare('I aM a BOy','abCdeFghijkLmnopqrStuVwxyzzwwtyyujjgfd')
    Traceback (most recent call last):
        ...
    KeyError: 'Length of alphabet has to be 27.'

    Testing with punctuation not in the given alphabet

    >>> __prepare('am i a boy?','abCdeFghijkLmnopqrStuVwxYZ+')
    Traceback (most recent call last):
        ...
    ValueError: Each message character has to be included in alphabet!

    Testing with numbers

    >>> __prepare(500,'abCdeFghijkLmnopqrStuVwxYZ+')
    Traceback (most recent call last):
        ...
    AttributeError: 'int' object has no attribute 'replace'
    """
    # Validate message and alphabet, set to upper and remove spaces
    alphabet = alphabet.replace(" ", "").upper()
    message = message.replace(" ", "").upper()

    # Check length and characters
    if len(alphabet) != 27:
        raise KeyError("Length of alphabet has to be 27.")
    if any(char not in alphabet for char in message):
        raise ValueError("Each message character has to be included in alphabet!")

    # Generate dictionares
    character_to_number = dict(zip(alphabet, TEST_CHARACTER_TO_NUMBER.values()))
    number_to_character = {
        number: letter for letter, number in character_to_number.items()
    }