diff -r ed091424f230 Doc/library/functions.rst
--- a/Doc/library/functions.rst	Sat Nov 03 17:51:25 2012 +0200
+++ b/Doc/library/functions.rst	Sat Nov 03 16:15:24 2012 -0400
@@ -934,6 +934,36 @@
    (*file*, *flags*). *opener* must return an open file descriptor (passing
    :mod:`os.open` as *opener* results in functionality similar to passing
    ``None``).
+  
+   The following example is an alternative implementation for opening files
+   for exclusive writing. Instead of passing ``'x'`` as the *mode*, we
+   create an open_exclusive function and use it as the *opener*::
+
+      >>> import os 
+      >>> def open_exclusive(path, mode):
+      ...     return os.open(path, mode | os.O_CREAT | os.O_EXCL)
+      ...
+      >>> filename = "/tmp/somefile"
+      >>> fp = open(filename, 'w', opener=open_exclusive)
+      >>> fp2 = open(filename, 'w', opener=open_exclusive)
+      Traceback (most recent call last):
+        File "<stdin>", line 1, in <module>
+        File "<stdin>", line 1, in <lambda>
+      FileExistsError: [Errno 17] File exists: '/tmp/somefile'
+
+   This other example uses the ``dir_fd`` parameter of the :mod:`os.open` 
+   function to open a file relative to a given directory::
+
+      >>> import os
+      >>> def open_at(dirname):
+      ...     dir_fd = os.open(dirname, os.O_RDONLY)
+      ...     def opener(path, flags):
+      ...         return os.open(path, flags, dir_fd=dir_fd)
+      ...     return opener
+      ...
+      >>> with open("testfile", "w", opener=open_at("/tmp/somedir")) as f:
+      ...     f.write("This will be written in the /tmp/somedir/testfile file.")
+      ...
 
    .. versionchanged:: 3.3
       The *opener* parameter was added.
diff -r ed091424f230 Doc/library/io.rst
--- a/Doc/library/io.rst	Sat Nov 03 17:51:25 2012 +0200
+++ b/Doc/library/io.rst	Sat Nov 03 16:15:24 2012 -0400
@@ -498,6 +498,9 @@
    :mod:`os.open` as *opener* results in functionality similar to passing
    ``None``).
 
+   See the :meth:`open()` built-in function for examples on using the *opener*
+   parameter. 
+
    .. versionchanged:: 3.3
       The *opener* parameter was added.
       The ``'x'`` mode was added.