Index: Lib/test/test_float.py
===================================================================
--- Lib/test/test_float.py	(Revision 67177)
+++ Lib/test/test_float.py	(Arbeitskopie)
@@ -117,6 +117,17 @@
         self.assertRaises(OverflowError, float('-inf').as_integer_ratio)
         self.assertRaises(ValueError, float('nan').as_integer_ratio)
 
+    def test_float_containment(self):
+        floats = (INF, -INF, 0.0, 1.0, NAN)
+        for f in floats:
+            self.assert_(f in [f], "'%r' not in []" % f)
+            self.assert_(f in (f,), "'%r' not in ()" % f)
+            self.assert_(f in {f}, "'%r' not in set()" % f)
+            self.assert_(f in {f: None}, "'%r' not in {}" % f)
+            self.assertEqual([f].count(f), 1, "[].count('%r') != 1" % f)
+            self.assert_(f in floats, "'%r' not in container" % f)
+
+
 class FormatFunctionsTestCase(unittest.TestCase):
 
     def setUp(self):