diff -r 19b2c54e5f09 Doc/library/pty.rst
--- a/Doc/library/pty.rst	Wed Nov 12 10:23:44 2014 -0500
+++ b/Doc/library/pty.rst	Thu Nov 13 13:00:21 2014 -0500
@@ -43,0 +43,0 @@

    The functions *master_read* and *stdin_read* should be functions which read from
    a file descriptor. The defaults try to read 1024 bytes each time they are
-   called.
+   called. Returning an empty string or any falsey value will be interpreted as 
+   an EOF condition. In order to silently ignore input or output, a null byte
+   ("\0") should be returned from the appropriate *_read* function.

    .. versionchanged:: 3.4
       :func:`spawn` now returns the status value from :func:`os.waitpid`