Learn String Manipulation by Building a Cipher - Step 81

Python
1

Tell us what’s happening:

Describe your issue in detail here.

Your code so far

text = 'Hello Zaira!'
custom_key = 'python'

def vigenere(message, key, direction=1):
    key_index = 0
    alphabet = 'abcdefghijklmnopqrstuvwxyz'
    final_message = ''

    for char in message.lower():

        # Append any non-letter character to the message
        if not char.isalpha():
            final_message += char
        else:        
            # Find the right key character to encode/decode
            key_char = key[key_index % len(key)]
            key_index += 1

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

# User Editable Region

def encrypt(message, key):
    return vigenere(message, key)
    
def decrypt(message, key):
    return vigenere(message, key, -1)
    
encryption = encrypt(message,key)
print(encryption)
decryption = decrypt(message,key)
print(decryption)

# User Editable Region

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Challenge Information:

Learn String Manipulation by Building a Cipher - Step 81

2

You appear to have created this post without editing the template. Please edit your post to Tell us what’s happening in your own words.

3

I am changing the cncrytion and decrytion to encrypt and decrypt but its not helping , am i not understanding

4

You appear to have created this post without editing the template. Please edit your post to Tell us what’s happening in your own words.

5

There are different kinds of variables here, Variables, Arguments and Parameters.

Variables:

text = 'Hello Zaira!'
custom_key = 'python'

Here you set up two variables containing strings of text. These are global variables.

def encrypt(message, key):
    return vigenere(message, key)

Here you set up a function with 2 parameters. These parameters message and key become variables that are accessible only within the function. They do not exist outside the function, or are at least inaccessible.

encryption = encrypt(message,key)

You cannot send message to the encrypt function, since it does not exist outside the function. Look at the original code again:

encryption = vigenere(text, custom_key)

It is passing the variables text and custom_key to the function as arguments. When they arrive at the function they will become the parameters message and key. So, don’t change the arguments here.

text = 'Hello Zaira!' #`text` is a plain sentence, not encrypted.
encryption = vigenere(text, custom_key) #text is sent to the function and is encrypted
decryption = vigenere(encryption, custom_key, -1) #the encrypted message is sent to the decryption function

You would not send the same variable to encryption and decryption.

TLDR:
Only change the name of the function being called. Don’t change the variables being sent as arguments). Watch out that decrypt only takes 2 arguments.

1 Like
6

Okey Thanks for your contribution

7

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