diff --git a/Doc/library/contextlib.rst b/Doc/library/contextlib.rst
--- a/Doc/library/contextlib.rst
+++ b/Doc/library/contextlib.rst
@@ -31,32 +31,38 @@ Functions and classes provided:
 
 
 .. decorator:: contextmanager
 
    This function is a :term:`decorator` that can be used to define a factory
    function for :keyword:`with` statement context managers, without needing to
    create a class or separate :meth:`__enter__` and :meth:`__exit__` methods.
 
-   A simple example (this is not recommended as a real way of generating HTML!)::
+   A simple example::
 
       from contextlib import contextmanager
 
       @contextmanager
-      def tag(name):
-          print("<%s>" % name)
-          yield
-          print("</%s>" % name)
+      def swap_attr(obj, attr, val):
+          old_val = getattr(obj, attr)
+          setattr(obj, attr, val)
+          try:
+              yield
+          finally:
+              setattr(obj, attr, old_val)
 
-      >>> with tag("h1"):
-      ...    print("foo")
+   Example usage of the ``swap_attr`` context manager::
+
+      >>> import string
+      >>> with swap_attr(string, 'ascii_letters', 'spameggs'):
+      ...     print(string.ascii_letters)
       ...
-      <h1>
-      foo
-      </h1>
+      spameggs
+      >>> print(string.ascii_letters)
+      abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
 
    The function being decorated must return a :term:`generator`-iterator when
    called. This iterator must yield exactly one value, which will be bound to
    the targets in the :keyword:`with` statement's :keyword:`as` clause, if any.
 
    At the point where the generator yields, the block nested in the :keyword:`with`
    statement is executed.  The generator is then resumed after the block is exited.
    If an unhandled exception occurs in the block, it is reraised inside the