Merged revisions 84814 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r84814 | antoine.pitrou | 2010-09-14 20:37:24 +0200 (mar., 14 sept. 2010) | 4 lines

  Issue #9854: The default read() implementation in io.RawIOBase now
  handles non-blocking readinto() returning None correctly.
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diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index f3cd261..7ae656e 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -371,8 +371,9 @@
 
    .. method:: readinto(b)
 
-      Read up to len(b) bytes into bytearray *b* and return the number of bytes
-      read.
+      Read up to len(b) bytes into bytearray *b* and return the number ofbytes
+      read.  If the object is in non-blocking mode and no bytes are available,
+      ``None`` is returned.
 
    .. method:: write(b)