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Task/Vigen-re-cipher/Python/vigen-re-cipher.py

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+'''Vigenere encryption and decryption'''
+
+from itertools import starmap, cycle
+
+
+def encrypt(message, key):
+    '''Vigenere encryption of message using key.'''
+
+    # Converted to uppercase.
+    # Non-alpha characters stripped out.
+    message = filter(str.isalpha, message.upper())
+
+    def enc(c, k):
+        '''Single letter encryption.'''
+
+        return chr(((ord(k) + ord(c) - 2 * ord('A')) % 26) + ord('A'))
+
+    return ''.join(starmap(enc, zip(message, cycle(key))))
+
+
+def decrypt(message, key):
+    '''Vigenere decryption of message using key.'''
+
+    def dec(c, k):
+        '''Single letter decryption.'''
+
+        return chr(((ord(c) - ord(k) - 2 * ord('A')) % 26) + ord('A'))
+
+    return ''.join(starmap(dec, zip(message, cycle(key))))
+
+
+def main():
+    '''Demonstration'''
+
+    text = 'Beware the Jabberwock, my son! The jaws that bite, ' + (
+           'the claws that catch!'
+    )
+    key = 'VIGENERECIPHER'
+
+    encr = encrypt(text, key)
+    decr = decrypt(encr, key)
+
+    print(text)
+    print(encr)
+    print(decr)
+
+
+if __name__ == '__main__':
+    main()