diff -r af18829a7754 Doc/library/doctest.rst
--- a/Doc/library/doctest.rst	Wed Jul 17 01:22:45 2013 +0200
+++ b/Doc/library/doctest.rst	Tue Jul 16 23:30:01 2013 -0500
@@ -278,6 +278,9 @@
 Any classes found are recursively searched similarly, to test docstrings in
 their contained methods and nested classes.
 
+.. versionchanged:: 3.4
+   Extension modules are now fully searched as well.
+
 
 .. _doctest-finding-examples:
 
@@ -1286,8 +1289,8 @@
    A processing class used to extract the :class:`DocTest`\ s that are relevant to
    a given object, from its docstring and the docstrings of its contained objects.
    :class:`DocTest`\ s can currently be extracted from the following object types:
-   modules, functions, classes, methods, staticmethods, classmethods, and
-   properties.
+   modules, functions, built-in functions, classes, methods, method descriptors
+   (built-in methods), staticmethods, classmethods, and properties.
 
    The optional argument *verbose* can be used to display the objects searched by
    the finder.  It defaults to ``False`` (no output).
@@ -1341,6 +1344,11 @@
       specified, or ``{}`` otherwise.  If *extraglobs* is not specified, then it
       defaults to ``{}``.
 
+   .. versionchanged:: 3.4
+      :class:`DocTestFinder` can now find doctests in the docstrings of
+      built-in functions and methods.
+
+
 
 .. _doctest-doctestparser:
 
diff -r af18829a7754 Lib/doctest.py
--- a/Lib/doctest.py	Wed Jul 17 01:22:45 2013 +0200
+++ b/Lib/doctest.py	Tue Jul 16 23:30:01 2013 -0500
@@ -918,6 +918,8 @@
             return module is inspect.getmodule(object)
         elif inspect.isfunction(object):
             return module.__dict__ is object.__globals__
+        elif inspect.ismethoddescriptor(object):
+            return module.__name__ == object.__objclass__.__module__
         elif inspect.isclass(object):
             return module.__name__ == object.__module__
         elif hasattr(object, '__module__'):
@@ -950,7 +952,7 @@
             for valname, val in obj.__dict__.items():
                 valname = '%s.%s' % (name, valname)
                 # Recurse to functions & classes.
-                if ((inspect.isfunction(val) or inspect.isclass(val)) and
+                if ((inspect.isroutine(val) or inspect.isclass(val)) and
                     self._from_module(module, val)):
                     self._find(tests, val, valname, module, source_lines,
                                globs, seen)
@@ -962,9 +964,8 @@
                     raise ValueError("DocTestFinder.find: __test__ keys "
                                      "must be strings: %r" %
                                      (type(valname),))
-                if not (inspect.isfunction(val) or inspect.isclass(val) or
-                        inspect.ismethod(val) or inspect.ismodule(val) or
-                        isinstance(val, str)):
+                if not (inspect.isroutine(val) or inspect.isclass(val) or
+                        inspect.ismodule(val) or isinstance(val, str)):
                     raise ValueError("DocTestFinder.find: __test__ values "
                                      "must be strings, functions, methods, "
                                      "classes, or modules: %r" %
@@ -983,7 +984,7 @@
                     val = getattr(obj, valname).__func__
 
                 # Recurse to methods, properties, and nested classes.
-                if ((inspect.isfunction(val) or inspect.isclass(val) or
+                if ((inspect.isroutine(val) or inspect.isclass(val) or
                       isinstance(val, property)) and
                       self._from_module(module, val)):
                     valname = '%s.%s' % (name, valname)
diff -r af18829a7754 Lib/test/test_builtin.py
--- a/Lib/test/test_builtin.py	Wed Jul 17 01:22:45 2013 +0200
+++ b/Lib/test/test_builtin.py	Tue Jul 16 23:30:01 2013 -0500
@@ -1595,21 +1595,10 @@
         data = 'The quick Brown fox Jumped over The lazy Dog'.split()
         self.assertRaises(TypeError, sorted, data, None, lambda x,y: 0)
 
-def test_main(verbose=None):
-    test_classes = (BuiltinTest, TestSorted)
-
-    run_unittest(*test_classes)
-
-    # verify reference counting
-    if verbose and hasattr(sys, "gettotalrefcount"):
-        import gc
-        counts = [None] * 5
-        for i in range(len(counts)):
-            run_unittest(*test_classes)
-            gc.collect()
-            counts[i] = sys.gettotalrefcount()
-        print(counts)
-
+def load_tests(loader, tests, pattern):
+    from doctest import DocTestSuite
+    tests.addTest(DocTestSuite(builtins))
+    return tests
 
 if __name__ == "__main__":
-    test_main(verbose=True)
+    unittest.main()
diff -r af18829a7754 Lib/test/test_doctest.py
--- a/Lib/test/test_doctest.py	Wed Jul 17 01:22:45 2013 +0200
+++ b/Lib/test/test_doctest.py	Tue Jul 16 23:30:01 2013 -0500
@@ -644,6 +644,31 @@
     >>> test = doctest.DocTestFinder().find(f)[0]
     >>> [e.lineno for e in test.examples]
     [1, 9, 12]
+
+Finding Doctests in Extension Modules
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+DocTestFinder can also find doctests in extension modules.  builtins isn't
+really an extension module, but it's written in C and guaranteed to be there,
+so we'll use it anyway.
+
+    >>> import builtins
+    >>> tests = doctest.DocTestFinder().find(builtins)
+    >>> len(tests) # how many objects checked for doctests
+    795
+    >>> real_tests = [t for t in tests if len(t.examples) > 0]
+    >>> len(real_tests) # how many objects actually have doctests
+    8
+    >>> for t in real_tests:
+    ...     print('{}  {}'.format(len(t.examples), t.name))
+    ...
+    1  builtins.bin
+    3  builtins.float.as_integer_ratio
+    2  builtins.float.fromhex
+    2  builtins.float.hex
+    1  builtins.hex
+    1  builtins.int
+    2  builtins.int.bit_length
+    1  builtins.oct
 """
 
 def test_DocTestParser(): r"""
diff -r af18829a7754 Objects/floatobject.c
--- a/Objects/floatobject.c	Wed Jul 17 01:22:45 2013 +0200
+++ b/Objects/floatobject.c	Tue Jul 16 23:30:01 2013 -0500
@@ -1416,7 +1416,7 @@
 >>> float.fromhex('0x1.ffffp10')\n\
 2047.984375\n\
 >>> float.fromhex('-0x1p-1074')\n\
--4.9406564584124654e-324");
+-5e-324");
 
 
 static PyObject *
diff -r af18829a7754 Python/bltinmodule.c
--- a/Python/bltinmodule.c	Wed Jul 17 01:22:45 2013 +0200
+++ b/Python/bltinmodule.c	Tue Jul 16 23:30:01 2013 -0500
@@ -340,7 +340,11 @@
 PyDoc_STRVAR(bin_doc,
 "bin(number) -> string\n\
 \n\
-Return the binary representation of an integer.");
+Return the binary representation of an integer.\n\
+\n\
+   >>> bin(2796202)\n\
+   '0b1010101010101010101010'\n\
+");
 
 
 static PyObject *
@@ -1263,7 +1267,11 @@
 PyDoc_STRVAR(hex_doc,
 "hex(number) -> string\n\
 \n\
-Return the hexadecimal representation of an integer.");
+Return the hexadecimal representation of an integer.\n\
+\n\
+   >>> hex(3735928559)\n\
+   '0xdeadbeef'\n\
+");
 
 
 static PyObject *
@@ -1463,7 +1471,11 @@
 PyDoc_STRVAR(oct_doc,
 "oct(number) -> string\n\
 \n\
-Return the octal representation of an integer.");
+Return the octal representation of an integer.\n\
+\n\
+   >>> oct(342391)\n\
+   '0o1234567'\n\
+");
 
 
 static PyObject *