Added Dequeue in Python

ciphers/caesar_cipher.py

@@ -0,0 +1,44 @@
+# The Caesar Cipher Algorithm
+
+def main():
+    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"
+
+    translated = encdec(message, key, mode)
+    if mode ==   "encrypt":
+        print("Encryption:", translated)
+    elif mode == "decrypt":
+        print("Decryption:", translated)
+        
+def encdec(message, key, mode):
+    message    = message.upper()
+    translated = ""
+    LETTERS    = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    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 -= len(LETTERS)
+            elif num < 0:
+                num += len(LETTERS)
+
+            translated += LETTERS[num]
+        else:
+            translated += symbol
+    return translated
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+    main()