range(len()) is almost always a hint to use enumerate()

Author: cclauss

Diff for: ciphers/running_key_cipher.py

@@ -1,3 +1,8 @@
+"""
+https://en.wikipedia.org/wiki/Running_key_cipher
+"""
+
+
 def running_key_encrypt(key: str, plaintext: str) -> str:
     """
     Encrypts the plaintext using the Running Key Cipher.
@@ -10,12 +15,13 @@ def running_key_encrypt(key: str, plaintext: str) -> str:
     key = key.replace(" ", "").upper()
     key_length = len(key)
     ciphertext = []
+    ord_a = ord("A")
 
-    for i in range(len(plaintext)):
-        p = ord(plaintext[i]) - ord("A")
-        k = ord(key[i % key_length]) - ord("A")
+    for i, char in enumerate(plaintext):
+        p = ord(char) - ord_a
+        k = ord(key[i % key_length]) - ord_a
         c = (p + k) % 26
-        ciphertext.append(chr(c + ord("A")))
+        ciphertext.append(chr(c + ord_a))
 
     return "".join(ciphertext)
 
@@ -32,23 +38,22 @@ def running_key_decrypt(key: str, ciphertext: str) -> str:
     key = key.replace(" ", "").upper()
     key_length = len(key)
     plaintext = []
+    ord_a = ord("A")
 
-    for i in range(len(ciphertext)):
-        c = ord(ciphertext[i]) - ord("A")
-        k = ord(key[i % key_length]) - ord("A")
+    for i, char in enumerate(ciphertext):
+        c = ord(char) - ord_a
+        k = ord(key[i % key_length]) - ord_a
         p = (c - k) % 26
-        plaintext.append(chr(p + ord("A")))
+        plaintext.append(chr(p + ord_a))
 
     return "".join(plaintext)
 
 
 def test_running_key_encrypt() -> None:
     """
     >>> key = "How does the duck know that? said Victor"
-    >>> plaintext = "DEFEND THIS"
-    >>> ciphertext = running_key_encrypt(key, plaintext)
-    >>> decrypted_text = running_key_decrypt(key, ciphertext)
-    >>> decrypted_text == "DEFENDTHIS"
+    >>> ciphertext = running_key_encrypt(key, "DEFEND THIS")
+    >>> running_key_decrypt(key, ciphertext) == "DEFENDTHIS"
     True
     """
 
@@ -59,11 +64,12 @@ def test_running_key_encrypt() -> None:
     doctest.testmod()
     test_running_key_encrypt()
 
-    key = "How does the duck know that? said Victor"
     plaintext = input("Enter the plaintext: ").upper()
+    print(f"\n{plaintext = }")
+
+    key = "How does the duck know that? said Victor"
     encrypted_text = running_key_encrypt(key, plaintext)
-    decrypted_text = running_key_decrypt(key, encrypted_text)
+    print(f"{encrypted_text = }")
 
-    print("\nPlaintext:", plaintext)
-    print("Encrypted:", encrypted_text)
-    print("Decrypted:", decrypted_text)
+    decrypted_text = running_key_decrypt(key, encrypted_text)
+    print(f"{decrypted_text = }")