diff -r 74d182cf0187 Doc/library/functions.rst
--- a/Doc/library/functions.rst	Wed Nov 30 00:25:06 2011 +0200
+++ b/Doc/library/functions.rst	Tue Nov 29 22:56:20 2011 -0500
@@ -961,6 +961,12 @@
    The *file* argument must be an object with a ``write(string)`` method; if it
    is not present or ``None``, :data:`sys.stdout` will be used.
 
+   The default encoding used for the various system streams (:data:`sys.stdin`, 
+   :data:`sys.stdout`, :data:`sys.stderr`) is set to the value of 
+   :envvar:`PYTHONIOENCODING` if defined, or if it isn't defined it is retrieved from 
+   the standard stream via :func:`os.device_encoding` or :func:`locale.getpreferredencoding`.
+
+   If the above fails the encoding defaults to ASCII.
 
 .. function:: property(fget=None, fset=None, fdel=None, doc=None)