Caesar_cipher.py

class main:
    def __init__(self, key: dict) -> None:
        self.key = key

    def get_input(self) -> None:
        while True:
            blank_string = str(input("Enter string to decrypt: "))
            if blank_string.isalpha():
                blank_string = blank_string.lower()
                self.blank_string = blank_string
                break
            else:
                print("Input is not valid")
                continue

    def encrypt_string(self) -> str:
        output = ""
        for c in self.blank_string:
            for k, v in self.key.items():
                if k == c:
                    output += v
                else:
                    continue
        self.decrypted_string = output
        return output

    def decrypt_string(self, string: str) -> str:
        output = ""
        string = string.lower()
        string = string.strip()
        if string == "":
            return self.blank_string
        else:
            for c in string:
                for k, v in self.key.items():
                    if v == c:
                        output += k

        return output


if __name__ == "__main__":
    key = {
        "a": "d",
        "b": "e",
        "c": "f",
        "d": "g",
        "e": "h",
        "f": "i",
        "g": "j",
        "h": "k",
        "i": "l",
        "j": "m",
        "k": "n",
        "l": "o",
        "m": "p",
        "n": "q",
        "o": "r",
        "p": "s",
        "q": "t",
        "r": "u",
        "s": "v",
        "t": "w",
        "u": "x",
        "v": "y",
        "w": "z",
        "x": "a",
        "y": "b",
        "z": "c",
    }
    main = main(key=key)
    main.get_input()
    print(main.encrypt_string())