add caesarCipher.py

caesarCipher.py

@@ -0,0 +1,29 @@
+import string
+
+def caesarCipher(message, key, mode):
+    SYMBOLS = string.ascii_uppercase + string.ascii_lowercase + string.digits + ' !?.'
+    translated = ''
+    for symbol in message :
+        if symbol in SYMBOLS:
+            symbolIndex = SYMBOLS.find(symbol)
+            if mode == 'encrypt':
+                translatedIndex = symbolIndex + key
+            elif mode == 'decrypt':
+                translatedIndex = symbolIndex - key
+
+            if translatedIndex >= len(SYMBOLS):
+                translatedIndex = translatedIndex - len(SYMBOLS)
+            elif translatedIndex < 0:
+                translatedIndex = translatedIndex + len(SYMBOLS)
+
+            translated = translated + SYMBOLS[translatedIndex]
+        else:
+            translated = translated + symbol
+    print(translated)
+
+if __name__ == '__main__':
+    message = 'This is my secret message.'
+    key = 13
+    mode = 'decrypt'
+    caesarCipher(message, key, mode)
+