=== modified file 'twisted/python/test/test_util.py'
--- twisted/python/test/test_util.py	2010-08-02 17:16:05 +0000
+++ twisted/python/test/test_util.py	2010-09-17 21:11:55 +0000
@@ -616,6 +616,149 @@
 
 
 
+class Hashable(util.FancyHashMixin):
+    compareAttributes = hashAttributes = ("value",)
+    def __init__(self, value):
+        self.value = value
+
+
+
+class DifferentHashable(util.FancyHashMixin):
+    compareAttributes = hashAttributes = ("value",)
+    def __init__(self, value):
+        self.value = value
+
+
+
+class PartialHashable(util.FancyHashMixin):
+    compareAttributes = ("valueOne", "valueTwo")
+    hashAttributes = ("valueOne",)
+
+    def __init__(self, valueOne, valueTwo):
+        self.valueOne, self.valueTwo = valueOne, valueTwo
+
+
+
+class DifferentPartialHashable(util.FancyHashMixin):
+    compareAttributes = ("valueOne", "valueTwo")
+    hashAttributes = ("valueOne",)
+
+    def __init__(self, valueOne, valueTwo):
+        self.valueOne, self.valueTwo = valueOne, valueTwo
+
+
+
+class FancyHashMixinTests(unittest.TestCase):
+    def test_equality(self):
+        h1, h2 = Hashable(1), Hashable(1)
+        self.assertEqual(h1, h1)
+        self.assertEqual(h1, h2)
+
+
+    def test_inequality(self):
+        h1, h2 = Hashable(1), Hashable(2)
+        self.assertNotEqual(h1, h2)
+
+
+    def test_inequality_differentClasses(self):
+        h1, h2 = Hashable(1), DifferentHashable(2)
+        self.assertNotEqual(h1, h2)
+
+
+    def test_hashConsistent(self):
+        h = Hashable(1)
+        self.assertEqual(hash(h), hash(h))
+
+
+    def test_hashEqual(self):
+        h1, h2 = Hashable(1), Hashable(1)
+        self.assertEqual(hash(h1), hash(h2))
+
+
+    def test_hashEqual_differentClasses(self):
+        h1, h2 = Hashable(1), DifferentHashable(1)
+        self.assertEqual(hash(h1), hash(h2))
+
+
+    def test_hashNotEqual(self):
+        h1, h2 = Hashable(1), Hashable(2)
+        self.assertNotEqual(hash(h1), hash(h2))
+
+
+    def test_hashNotEqual_differentClasses(self):
+        h1, h2 = Hashable(1), DifferentHashable(2)
+        self.assertNotEqual(hash(h1), hash(h2))
+
+
+    def test_set(self):
+        s = set([Hashable(1), Hashable(1)])
+        self.assertEqual(len(s), 1)
+
+
+
+class PartialHashableTests(unittest.TestCase):
+    def test_equality(self):
+        h1, h2 = PartialHashable(1, 2), PartialHashable(1, 2)
+        self.assertEqual(h1, h1)
+        self.assertEqual(h1, h2)
+
+
+    def test_inequality(self):
+        h1, h2 = PartialHashable(1, 2), PartialHashable(2, 1)
+        self.assertNotEqual(h1, h2)
+
+
+    def test_hashConsistent(self):
+        h = PartialHashable(1, 2)
+        self.assertEqual(hash(h), hash(h))
+
+
+    def test_hashEqual(self):
+        h1, h2 = PartialHashable(1, 2), PartialHashable(1, 2)
+        self.assertEqual(hash(h1), hash(h2))
+
+
+    def test_hashEqual_differentClasses(self):
+        h1, h2 = PartialHashable(1, 2), DifferentPartialHashable(1, 2)
+        self.assertEqual(hash(h1), hash(h2))
+
+
+    def test_hashEqual_partial(self):
+        h1, h2 = PartialHashable(1, 1), PartialHashable(1, 2)
+        self.assertEqual(hash(h1), hash(h2))
+
+
+    def test_hashEqual_partial_differentClasses(self):
+        h1, h2 = PartialHashable(1, 1), DifferentPartialHashable(1, 2)
+        self.assertEqual(hash(h1), hash(h2))
+
+
+    def test_hashNotEqual(self):
+        h1, h2 = PartialHashable(1, 2), PartialHashable(2, 1)
+        self.assertNotEqual(hash(h1), hash(h2))
+
+
+    def test_hashNotEqual_differentClasses(self):
+        h1, h2 = PartialHashable(1, 2), PartialHashable(2, 1)
+        self.assertNotEqual(hash(h1), hash(h2))
+
+
+    def test_set(self):
+        s = set([PartialHashable(1, 2), PartialHashable(1, 2)])
+        self.assertEqual(len(s), 1)
+
+
+    def test_set_equalHashes(self):
+        s = set([PartialHashable(1, 1), PartialHashable(1, 2)])
+        self.assertEqual(len(s), 2)
+
+
+    def test_set_equalHashes_differentClasses(self):
+        s = set([PartialHashable(1, 2), DifferentPartialHashable(1, 2)])
+        self.assertEqual(len(s), 2)
+
+
+
 class RunAsEffectiveUserTests(unittest.TestCase):
     """
     Test for the L{util.runAsEffectiveUser} function.

=== modified file 'twisted/python/util.py'
--- twisted/python/util.py	2010-08-02 17:16:05 +0000
+++ twisted/python/util.py	2010-09-17 21:14:34 +0000
@@ -563,6 +563,18 @@
         return not result
 
 
+    __hash__ = None
+
+
+
+class FancyHashMixin(FancyEqMixin):
+    compareAttributes = hashAttributes = ()
+
+    def __hash__(self):
+        values = tuple(getattr(self, name) for name in self.hashAttributes)
+        return hash(values)
+
+
 
 def dsu(list, key):
     """