bpo-35712: Make using NotImplemented in a boolean context issue a deprecation warning (GH-13195)
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 5b3b669..8be432d 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -156,13 +156,18 @@
object is accessed through the built-in name ``NotImplemented``. Numeric methods
and rich comparison methods should return this value if they do not implement the
operation for the operands provided. (The interpreter will then try the
- reflected operation, or some other fallback, depending on the operator.) Its
- truth value is true.
+ reflected operation, or some other fallback, depending on the operator.) It
+ should not be evaluated in a boolean context.
See
:ref:`implementing-the-arithmetic-operations`
for more details.
+ .. versionchanged:: 3.9
+ Evaluating ``NotImplemented`` in a boolean context is deprecated. While
+ it currently evaluates as true, it will emit a :exc:`DeprecationWarning`.
+ It will raise a :exc:`TypeError` in a future version of Python.
+
Ellipsis
.. index::