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def remove_duplicates(key: str) -> str:

"""

Removes duplicate alphabetic characters in a keyword (letter is ignored after its

first appearance).

:param key: Keyword to use

:return: String with duplicates removed

>>> remove_duplicates('Hello World!!')

'Helo Wrd'

"""

key_no_dups = ""

for ch in key:

if ch == " " or ch not in key_no_dups and ch.isalpha():

key_no_dups += ch

return key_no_dups

def create_cipher_map(key: str) -> dict:

"""

Returns a cipher map given a keyword.

:param key: keyword to use

:return: dictionary cipher map

"""

# Create alphabet list

alphabet = [chr(i + 65) for i in range(26)]

# Remove duplicate characters from key

key = remove_duplicates(key.upper())

offset = len(key)

# First fill cipher with key characters

cipher_alphabet = {alphabet[i]: char for i, char in enumerate(key)}

# Then map remaining characters in alphabet to

# the alphabet from the beginning

for i in range(len(cipher_alphabet), 26):

char = alphabet[i - offset]

# Ensure we are not mapping letters to letters previously mapped

while char in key:

offset -= 1

char = alphabet[i - offset]

cipher_alphabet[alphabet[i]] = char

return cipher_alphabet

def encipher(message: str, cipher_map: dict) -> str:

"""

Enciphers a message given a cipher map.

:param message: Message to encipher

:param cipher_map: Cipher map

:return: enciphered string

>>> encipher('Hello World!!', create_cipher_map('Goodbye!!'))

'CYJJM VMQJB!!'

"""

return "".join(cipher_map.get(ch, ch) for ch in message.upper())

def decipher(message: str, cipher_map: dict) -> str:

"""

Deciphers a message given a cipher map

:param message: Message to decipher

:param cipher_map: Dictionary mapping to use

:return: Deciphered string

>>> cipher_map = create_cipher_map('Goodbye!!')

>>> decipher(encipher('Hello World!!', cipher_map), cipher_map)

'HELLO WORLD!!'

"""

# Reverse our cipher mappings

rev_cipher_map = {v: k for k, v in cipher_map.items()}

return "".join(rev_cipher_map.get(ch, ch) for ch in message.upper())

def main():

"""

Handles I/O

:return: void

"""

message = input("Enter message to encode or decode: ").strip()

key = input("Enter keyword: ").strip()

option = input("Encipher or decipher? E/D:").strip()[0].lower()

try:

func = {"e": encipher, "d": decipher}[option]

except KeyError:

raise KeyError("invalid input option")

cipher_map = create_cipher_map(key)

print(func(message, cipher_map))

if __name__ == "__main__":

import doctest

doctest.testmod()

main()

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