#1582: document __reversed__, patch by Mark Russell.
diff --git a/Doc/ACKS.txt b/Doc/ACKS.txt
index 32943bd..7344cf8 100644
--- a/Doc/ACKS.txt
+++ b/Doc/ACKS.txt
@@ -158,6 +158,7 @@
* Jim Roskind
* Guido van Rossum
* Donald Wallace Rouse II
+ * Mark Russell
* Nick Russo
* Chris Ryland
* Constantina S.
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 4f86fc7..693af64 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -977,12 +977,16 @@
.. function:: reversed(seq)
- Return a reverse :term:`iterator`. *seq* must be an object which supports
- the sequence protocol (the :meth:`__len__` method and the :meth:`__getitem__`
- method with integer arguments starting at ``0``).
+ Return a reverse :term:`iterator`. *seq* must be an object which has
+ a :meth:`__reversed__` method or supports the sequence protocol (the
+ :meth:`__len__` method and the :meth:`__getitem__` method with integer
+ arguments starting at ``0``).
.. versionadded:: 2.4
+ .. versionchanged:: 2.6
+ Added the possibility to write a custom :meth:`__reversed__` method.
+
.. function:: round(x[, n])
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 7ea6ca7..ed05b32 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1796,6 +1796,22 @@
Iterator objects also need to implement this method; they are required to return
themselves. For more information on iterator objects, see :ref:`typeiter`.
+
+.. method:: object.__reversed__(self)
+
+ Called (if present) by the :func:`reversed` builtin to implement
+ reverse iteration. It should return a new iterator object that iterates
+ over all the objects in the container in reverse order.
+
+ If the :meth:`__reversed__` method is not provided, the
+ :func:`reversed` builtin will fall back to using the sequence protocol
+ (:meth:`__len__` and :meth:`__getitem__`). Objects should normally
+ only provide :meth:`__reversed__` if they do not support the sequence
+ protocol and an efficient implementation of reverse iteration is possible.
+
+ .. versionadded:: 2.6
+
+
The membership test operators (:keyword:`in` and :keyword:`not in`) are normally
implemented as an iteration through a sequence. However, container objects can
supply the following special method with a more efficient implementation, which