bpo-20092. Use __index__ in constructors of int, float and complex. (GH-13108)
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 44017d8..fa47bf1 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -2394,11 +2394,9 @@
functions). Presence of this method indicates that the numeric object is
an integer type. Must return an integer.
- .. note::
-
- In order to have a coherent integer type class, when :meth:`__index__` is
- defined :meth:`__int__` should also be defined, and both should return
- the same value.
+ If :meth:`__int__`, :meth:`__float__` and :meth:`__complex__` are not
+ defined then corresponding built-in functions :func:`int`, :func:`float`
+ and :func:`complex` fall back to :meth:`__index__`.
.. method:: object.__round__(self, [,ndigits])