Cryptography Algorithm

Caesar Cipher.py

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+# The Caesar Cipher Algorithm
+
+message = input("Enter message: ")
+key = int(input("Key [1-26]: "))
+mode = input("Encrypt or Decrypt [e/d]: ")
+
+if mode.lower().startswith('e'):
+    mode = "encrypt"
+elif mode.lower().startswith('d'):
+    mode = "decrypt"
+
+LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+translated = ""
+
+message = message.upper()
+
+for symbol in message:
+    if symbol in LETTERS:
+        num = LETTERS.find(symbol)
+        if mode == "encrypt":
+            num = num + key
+        elif mode == "decrypt":
+            num = num - key
+
+        if num >= len(LETTERS):
+            num = num - len(LETTERS)
+        elif num < 0:
+            num = num + len(LETTERS)
+
+        translated = translated + LETTERS[num]
+    else:
+        translated = translated + symbol
+
+if mode == "encrypt":
+    print("Encryption:", translated)
+elif mode == "decrypt":
+    print("Decryption:", translated)