Step 69, cant understand

Python
1

I know how to complete the step, can someone explain the code I’m confused.

text = 'Hello Zaira'
custom_key = 'python'

def vigenere(message, key):
    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) % len(alphabet)
            encrypted_text += alphabet[new_index]
    
    return encrypted_text

encryption = vigenere(text, custom_key)
print(encryption)
2

Please provide a link to the step and talk to us about how you are confused. Thanks

3

I don’t understand “key_char” and “key_index” what is their purpose

4

Do you know what the Vigenere cypher does? If not, a quick read of the Wikipedia article or similar would be super helpful.