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Diffstat (limited to 'Doc/reference/datamodel.rst')
| -rw-r--r-- | Doc/reference/datamodel.rst | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 6acd25a760..9c2d7cd584 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -1688,6 +1688,20 @@ container; for mappings, :meth:`__iter__` should be the same as 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. + + 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 |