diff --git a/solutions/python/all-unique-characters.py b/solutions/python/all-unique-characters.py
index 9224d9b..b7b96fc 100644
--- a/solutions/python/all-unique-characters.py
+++ b/solutions/python/all-unique-characters.py
@@ -3,8 +3,14 @@
 import unittest
 
 def all_unique(string):
+    
+    # Optimization that assumes only 256 (2^8) ASCII characters are possible (ignores possibility of unicode)
+    nLetters = len(letters)
+    if (nLetters > 256):
+        return False
+    
     letters = sorted(string)
-    for i in range(len(letters) - 1):
+    for i in range(nLetters - 1):
         if letters[i] == letters[i + 1]:
             return False
     return True