Index: Lib/urllib.py
===================================================================
--- Lib/urllib.py	(revision 78945)
+++ Lib/urllib.py	(working copy)
@@ -1158,20 +1158,17 @@
     if match: return match.group(1, 2)
     return attr, None
 
-_hextochr = dict(('%02x' % i, chr(i)) for i in range(256))
-_hextochr.update(('%02X' % i, chr(i)) for i in range(256))
-
 def unquote(s):
     """unquote('abc%20def') -> 'abc def'."""
     res = s.split('%')
     for i in xrange(1, len(res)):
         item = res[i]
         try:
-            res[i] = _hextochr[item[:2]] + item[2:]
-        except KeyError:
-            res[i] = '%' + item
+            res[i] = chr(int(item[:2], 16)) + item[2:]
         except UnicodeDecodeError:
             res[i] = unichr(int(item[:2], 16)) + item[2:]
+        except ValueError:
+            res[i] = '%' + item
     return "".join(res)
 
 def unquote_plus(s):
Index: Lib/test/test_urllib.py
===================================================================
--- Lib/test/test_urllib.py	(revision 78945)
+++ Lib/test/test_urllib.py	(working copy)
@@ -439,6 +439,32 @@
                          "using unquote(): not all characters escaped: "
                          "%s" % result)
 
+    def test_unquoting_badpercent(self):
+        # Test unquoting on bad percent-escapes
+        given = '%xab'
+        expect = given
+        result = urllib.unquote(given)
+        self.assertEqual(expect, result, "using unquote(): %r != %r"
+                         % (expect, result))
+        given = '%x'
+        expect = given
+        result = urllib.unquote(given)
+        self.assertEqual(expect, result, "using unquote(): %r != %r"
+                         % (expect, result))
+        given = '%'
+        expect = given
+        result = urllib.unquote(given)
+        self.assertEqual(expect, result, "using unquote(): %r != %r"
+                         % (expect, result))
+
+    def test_unquoting_mixed_case(self):
+        # Test unquoting on mixed-case hex digits in the percent-escapes
+        given = '%Ab%eA'
+        expect = '\xab\xea'
+        result = urllib.unquote(given)
+        self.assertEqual(expect, result, "using unquote(): %r != %r"
+                         % (expect, result))
+
     def test_unquoting_parts(self):
         # Make sure unquoting works when have non-quoted characters
         # interspersed