Python (Writing a function)

Reuse the functions we have defined during the lecture within a program that presents the following list of actions as a menu for a user:

1. enter a key;

2. encrypt a text input by the user;

3. decrypt a text input by the user;

4. read a file containing plaintext and write the encrypted text to another file;

5. read a file containing ciphertext and write the decrypted text to another file;

6. exit the program.

The key has to be provided by the user, even if your menu does not include action 1 (in this case actions 25 must incorporate action 1). The program will perform the action chosen by the user and, unless the user chooses to exit the program, will present again the list of action.

P.S. Code from the lecture:

def char_encrypt(c,shift): return chr(ord('A') + (ord(c.upper()) - ord('A') + shift) % 26)

def char_decrypt(c,shift): return chr(ord('a') + (ord(c.lower()) - ord('a') - shift) % 26)

def encrypt(plaintext, key): ciphertext = '' k_index = 0 for c in plaintext: if c.isalpha(): ciphertext = ciphertext + char_encrypt(c,key[k_index]) k_index = (k_index + 1) % len(key) else: ciphertext = ciphertext + c return ciphertext

def decrypt(ciphertext, key): plaintext = '' k_index = 0 for c in ciphertext: if c.isalpha(): plaintext = plaintext + char_decrypt(c,key[k_index]) k_index = (k_index + 1) % len(key) else: plaintext = plaintext + c return plaintext

plain_msg = 'My name is Adam Johnson' print(plain_msg) key_1 = [ 2, 4, 1, 6, 5 ] cipher_msg = encrypt(plain_msg,key_1) print(cipher_msg) decrypted_msg = decrypt(cipher_msg,key_1) print(decrypted_msg)