diff -r eaae4008327d Doc/library/functions.rst
--- a/Doc/library/functions.rst	Tue Feb 04 09:49:14 2014 +0100
+++ b/Doc/library/functions.rst	Tue Feb 04 13:20:36 2014 +0000
@@ -727,7 +727,7 @@
 .. function:: len(s)
 
    Return the length (the number of items) of an object.  The argument may be a
-   sequence (string, tuple or list) or a mapping (dictionary).
+   sequence (string, tuple or list), a mapping (dictionary), or a set.
 
 
 .. _func-list:
diff -r eaae4008327d Python/bltinmodule.c
--- a/Python/bltinmodule.c	Tue Feb 04 09:49:14 2014 +0100
+++ b/Python/bltinmodule.c	Tue Feb 04 13:20:36 2014 +0000
@@ -1327,7 +1327,7 @@
 PyDoc_STRVAR(len_doc,
 "len(module, object)\n\
 \n\
-Return the number of items of a sequence or mapping.");
+Return the number of items of a sequence or container.");
 
 
 static PyObject *