@@ -46,6 +46,24 @@ Rational number class.
    :class:`decimal.Decimal`.
 
 
+.. method:: Fraction.limit_denominator(max_denominator=1000000)
+
+   Finds and returns the closest :class:`Fraction` to ``self`` that
+   has denominator at most max_denominator.  This method is useful for
+   finding rational approximations to a given floating-point number::
+
+      >>> Fraction('3.1415926535897932').limit_denominator(1000)
+      Fraction(355, 113)
+
+   or for recovering a rational number that's represented as a float::
+
+      >>> from math import pi, cos
+      >>> Fraction.from_float(cos(pi/3))
+      Fraction(4503599627370497L, 9007199254740992L)
+      >>> Fraction.from_float(cos(pi/3)).limit_denominator()
+      Fraction(1, 2)
+
+
 .. method:: Fraction.__floor__()
 
    Returns the greatest :class:`int` ``<= self``. Will be accessible
 
@@ -1584,7 +1584,7 @@ written in Python, such as a mail server's external command delivery program.
    user time, children's system time, and elapsed real time since a fixed point in
    the past, in that order.  See the Unix manual page :manpage:`times(2)` or the
    corresponding Windows Platform API documentation. Availability: Macintosh, Unix,
-   Windows.
+   Windows.  On Windows, only the first two items are filled, the others are zero.
 
 
 .. function:: wait()
 
@@ -162,8 +162,19 @@ def _dump_registry(cls, file=None):
 
     def __instancecheck__(cls, instance):
         """Override for isinstance(instance, cls)."""
-        return any(cls.__subclasscheck__(c)
-                   for c in {instance.__class__, type(instance)})
+        # Inline the cache checking
+        subclass = instance.__class__
+        if subclass in cls._abc_cache:
+            return True
+        subtype = type(instance)
+        if subtype is subclass:
+            if (cls._abc_negative_cache_version ==
+                ABCMeta._abc_invalidation_counter and
+                subclass in cls._abc_negative_cache):
+                return False
+            # Fall back to the subclass check.
+            return cls.__subclasscheck__(subclass)
+        return any(cls.__subclasscheck__(c) for c in {subclass, subtype})
 
     def __subclasscheck__(cls, subclass):
         """Override for issubclass(subclass, cls)."""