Gronsfeld_cipher

ALPHABET: str = 'abcdefghijklmnopqrstuvwxyz'

def normalize_key_length(text: str, key: str): result: str = '' i: int = 0

for char in text:
    if ALPHABET.find(char.lower()) != -1:
        result += key[i % len(key)]
        i += 1
    else:
        result += ' '
return result

def encrypt(text: str, key: str): key: str = normalize_key_length(text, key) result: str = ''

for i in range(0, len(text)):
    position_in_alphabet = ALPHABET.find(text[i].lower())
    if position_in_alphabet == -1:
        result += text[i]
        continue

    slide: int = int(key[i])
    position_letter_for_replace = position_in_alphabet + slide
    letter_for_replace: str = ''
    if position_letter_for_replace >= len(ALPHABET):
        letter_for_replace = ALPHABET[position_letter_for_replace -
                                      len(ALPHABET)]
    else:
        letter_for_replace = ALPHABET[position_letter_for_replace]

    if text[i] != text[i].lower():
        letter_for_replace = letter_for_replace.upper()

    result += letter_for_replace

return result

def decrypt(text: str, key: str): key: str = normalize_key_length(text, key) result: str = ''

for i in range(0, len(text)):
    position_in_alphabet = ALPHABET.find(text[i].lower())
    if position_in_alphabet == -1:
        result += text[i]
        continue

    slide: int = int(key[i])
    position_letter_for_replace = position_in_alphabet - slide
    letter_for_replace: str = ''
    if position_letter_for_replace < 0:
        letter_for_replace = ALPHABET[position_letter_for_replace +
                                      len(ALPHABET)]
    else:
        letter_for_replace = ALPHABET[position_letter_for_replace]

    if text[i] != text[i].lower():
        letter_for_replace = letter_for_replace.upper()

    result += letter_for_replace

return result

text: str = input('Enter text: ') key = input('Enter key: ') encrypted: str = encrypt(text, key) print("Encrypted: ", encrypted) print("Decrypted: ", decrypt(encrypted, key))