freeCodeCamp/curriculum/challenges/german/07-scientific-computing-with-python/learn-string-manipulation-by-building-a-cipher/6554e0adc7bb193cbfdb36d5.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
6554e0adc7bb193cbfdb36d5	Step 73	20	step-73

--description--

Check if the function can decrypt the string back to the plain text.

Declare another variable called decryption and assign it vigenere(encryption, custom_key, -1).

--hints--

You should call vigenere passing encryption, custom_key and -1 as the arguments.

({ test: () => assert.match(code, /vigenere\s*\(\s*encryption\s*,\s*custom_key\s*,\s*-\s*1\s*\)/) })

You should declare a decryption variable.

({ test: () => assert(__userGlobals.has("decryption")) })

Your decryption variable should have the value of vigenere(encryption, custom_key, -1).

({ test: () => assert.match(code, /^decryption\s*=\s*vigenere\s*\(\s*encryption\s*,\s*custom_key\s*,\s*-\s*1\s*\)/m) })

--seed--

--seed-contents--

text = 'Hello Zaira'
custom_key = 'python'

def vigenere(message, key, direction):
    key_index = 0
    alphabet = 'abcdefghijklmnopqrstuvwxyz'
    encrypted_text = ''

    for char in message.lower():

        # Append space to the message
        if char == ' ':
            encrypted_text += char
        else:        
            # Find the right key character to encode
            key_char = key[key_index % len(key)]
            key_index += 1

            # Define the offset and the encrypted letter
            offset = alphabet.index(key_char)
            index = alphabet.find(char)
            new_index = (index + offset*direction) % len(alphabet)
            encrypted_text += alphabet[new_index]

    return encrypted_text
--fcc-editable-region--    
encryption = vigenere(text, custom_key, 1)
print(encryption)

--fcc-editable-region--