!usrbinenv python3 A Polybius Square is a table that allows someone to translate letters into numbers. https:www.braingle.combrainteaserscodespolybius.php Return the pair of numbers that represents the given letter in the polybius square  np.arrayequalPolybiusCipher.lettertonumbers'a', 1,1 True  np.arrayequalPolybiusCipher.lettertonumbers'u', 4,5 True Return the letter corresponding to the position index1, index2 in the polybius square  PolybiusCipher.numberstoletter4, 5  u True  PolybiusCipher.numberstoletter1, 1  a True Return the encoded version of message according to the polybius cipher  PolybiusCipher.encodetest message  44154344 32154343112215 True  PolybiusCipher.encodeTest Message  44154344 32154343112215 True Return the decoded version of message according to the polybius cipher  PolybiusCipher.decode44154344 32154343112215  test message True  PolybiusCipher.decode4415434432154343112215  testmessage True
#!/usr/bin/env python3

"""
A Polybius Square is a table that allows someone to translate letters into numbers.

https://www.braingle.com/brainteasers/codes/polybius.php
"""

import numpy as np

SQUARE = [
    ["a", "b", "c", "d", "e"],
    ["f", "g", "h", "i", "k"],
    ["l", "m", "n", "o", "p"],
    ["q", "r", "s", "t", "u"],
    ["v", "w", "x", "y", "z"],
]


class PolybiusCipher:
    def __init__(self) -> None:
        self.SQUARE = np.array(SQUARE)

    def letter_to_numbers(self, letter: str) -> np.ndarray:
        """
        Return the pair of numbers that represents the given letter in the
        polybius square
        >>> np.array_equal(PolybiusCipher().letter_to_numbers('a'), [1,1])
        True

        >>> np.array_equal(PolybiusCipher().letter_to_numbers('u'), [4,5])
        True
        """
        index1, index2 = np.where(letter == self.SQUARE)
        indexes = np.concatenate([index1 + 1, index2 + 1])
        return indexes

    def numbers_to_letter(self, index1: int, index2: int) -> str:
        """
        Return the letter corresponding to the position [index1, index2] in
        the polybius square

        >>> PolybiusCipher().numbers_to_letter(4, 5) == "u"
        True

        >>> PolybiusCipher().numbers_to_letter(1, 1) == "a"
        True
        """
        return self.SQUARE[index1 - 1, index2 - 1]

    def encode(self, message: str) -> str:
        """
        Return the encoded version of message according to the polybius cipher

        >>> PolybiusCipher().encode("test message") == "44154344 32154343112215"
        True

        >>> PolybiusCipher().encode("Test Message") == "44154344 32154343112215"
        True
        """
        message = message.lower()
        message = message.replace("j", "i")

        encoded_message = ""
        for letter_index in range(len(message)):
            if message[letter_index] != " ":
                numbers = self.letter_to_numbers(message[letter_index])
                encoded_message = encoded_message + str(numbers[0]) + str(numbers[1])
            elif message[letter_index] == " ":
                encoded_message = encoded_message + " "

        return encoded_message

    def decode(self, message: str) -> str:
        """
        Return the decoded version of message according to the polybius cipher

        >>> PolybiusCipher().decode("44154344 32154343112215") == "test message"
        True

        >>> PolybiusCipher().decode("4415434432154343112215") == "testmessage"
        True
        """
        message = message.replace(" ", "  ")
        decoded_message = ""
        for numbers_index in range(int(len(message) / 2)):
            if message[numbers_index * 2] != " ":
                index1 = message[numbers_index * 2]
                index2 = message[numbers_index * 2 + 1]

                letter = self.numbers_to_letter(int(index1), int(index2))
                decoded_message = decoded_message + letter
            elif message[numbers_index * 2] == " ":
                decoded_message = decoded_message + " "

        return decoded_message
