1 files changed, 5 insertions, 0 deletions
diff --git a/Lib/sets.py b/Lib/sets.py
index 2605c98..6d2c032 100644
--- a/Lib/sets.py
+++ b/Lib/sets.py
@@ -102,6 +102,11 @@ class BaseSet(object):
         """
         return self._data.iterkeys()
 
+    # Three-way comparison is not supported
+
+    def __cmp__(self, other):
+        raise TypeError, "can't compare sets using cmp()"
+
     # Equality comparisons using the underlying dicts
 
     def __eq__(self, other):