done

05-caesar-cipher/caesar.py

@@ -1,9 +1,24 @@
+def char_shift(char, shift):
+	start = 65 if char.isupper() else 97
+	char = ord(char) - start
+	shift = (char + shift) % 26
+	return chr(shift+start)
+
 def caesar(message, shift):
-	pass
+	out = ''
-
+	for letter in message:
-
+		if letter.isalpha():
-
+			letter = char_shift(letter, shift)
+		out += letter
 
+	return out
 
+def decrypt_caesar(message, shift):
+	return caesar(message, shift - (shift*2))
 
 # Add your own assert statements to test your code.
+
+sentence = 'But the Caesar Cipher is [still used](http://en.wikipedia.org/wiki/ROT13)'
+shift = 300
+
+assert(decrypt_caesar(caesar(sentence, shift), 300) == sentence )