feat: preserve case in encryption and decryption

Author: Darshan

Caesar_cipher.py

@@ -1,36 +1,43 @@
 alphabet = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
-def encryption(plain_text,shift_key):
+
+def encryption(plain_text, shift_key):
     cipher_text = ""
     for char in plain_text:
-        if char in alphabet:
-            position = alphabet.index(char)
-            new_position = (position+shift_key)%26
-            cipher_text += alphabet[new_position]
+        if char.lower() in alphabet:  # Check lowercase version of the character
+            is_upper = char.isupper()  # Check if the original character is uppercase
+            position = alphabet.index(char.lower())
+            new_position = (position + shift_key) % 26
+            new_char = alphabet[new_position]
+            cipher_text += new_char.upper() if is_upper else new_char  # Preserve original case
         else:
-            cipher_text += char
-    print(f"Here's is the text after encryption: {cipher_text}")
+            cipher_text += char  # Non-alphabet characters remain unchanged
+    print(f"Here's the text after encryption: {cipher_text}")
 
-def decryption(cipher_text,shift_key):
+def decryption(cipher_text, shift_key):
     plain_text = ""
     for char in cipher_text:
-        if char in alphabet:
-            position = alphabet.index(char)
-            new_position = (position-shift_key)%26
-            plain_text += alphabet[new_position]
+        if char.lower() in alphabet:  # Check lowercase version of the character
+            is_upper = char.isupper()  # Check if the original character is uppercase
+            position = alphabet.index(char.lower())
+            new_position = (position - shift_key) % 26
+            new_char = alphabet[new_position]
+            plain_text += new_char.upper() if is_upper else new_char  # Preserve original case
         else:
-            plain_text += char
-    print(f"Here's is the text after decryption: {plain_text}")
+            plain_text += char  # Non-alphabet characters remain unchanged
+    print(f"Here's the text after decryption: {plain_text}")
 
 end_program = False
-while not end_program:        
-    what_to_do = input("Type 'encrypt' for encryption, type 'decrypt' for decryption:\n")
-    text = input("Type your message:\n").lower()
+while not end_program:
+    what_to_do = input("Type 'encrypt' for encryption, type 'decrypt' for decryption:\n").lower()
+    text = input("Type your message:\n")  # No longer forcing lowercase here
     shift = int(input("Enter shift key:\n"))
-    if what_to_do=="encrypt":
+    if what_to_do == "encrypt":
         encryption(plain_text=text, shift_key=shift)
-    elif what_to_do=="decrypt":
+    elif what_to_do == "decrypt":
         decryption(cipher_text=text, shift_key=shift)
-    play_again = input("Type 'yes' to continue, type 'no' to exit.\n")
+    else:
+        print("Invalid option. Please type 'encrypt' or 'decrypt'.")
+    play_again = input("Type 'yes' to continue, type 'no' to exit.\n").lower()
     if play_again == 'no':
         end_program = True
-        print("Have a nice day! Bye..")
+        print("Have a nice day! Bye..")