Index: Lib/test/test_float.py
===================================================================
--- Lib/test/test_float.py	(revision 76596)
+++ Lib/test/test_float.py	(working copy)
@@ -490,7 +490,30 @@
         self.assertAlmostEqual(round(0.5e22, -22), 1e22)
         self.assertAlmostEqual(round(1.5e22, -22), 2e22)
 
+    @unittest.skipUnless(float.__getformat__("double").startswith("IEEE"),
+                         "test requires IEEE 754 doubles")
+    def test_format_specials(self):
+        # test formatting of nans and infs
+        nan = float('nan')
+        inf = float('inf')
+        for fmt in ['%e', '%f', '%g', '%.0e', '%.6f', '%.20g',
+                    '%#e', '%#f', '%#g', '%#.20e', '%#.15f', '%#.3g']:
+            pfmt = '%+' + fmt[1:]
+            sfmt = '% ' + fmt[1:]
+            self.assertEqual(fmt % inf, 'inf', fmt)
+            self.assertEqual(fmt % -inf, '-inf', fmt)
+            self.assertEqual(fmt % nan, 'nan', fmt)
+            self.assertEqual(fmt % -nan, 'nan', fmt)
+            # when a sign is asked for, it should be included
+            # for infinities, but not for nans
+            self.assertEqual(pfmt % inf, '+inf', pfmt)
+            self.assertEqual(pfmt % -inf, '-inf', pfmt)
+            self.assertEqual(pfmt % nan, '+nan', pfmt)
+            self.assertEqual(sfmt % inf, ' inf', sfmt)
+            self.assertEqual(sfmt % -inf, '-inf', sfmt)
+            self.assertEqual(sfmt % -nan, ' nan', sfmt)
 
+
 # Beginning with Python 2.6 float has cross platform compatible
 # ways to create and represent inf and nan
 class InfNanTest(unittest.TestCase):