bpo-20092. Use __index__ in constructors of int, float and complex. (GH-13108)

2 files changed, 11 insertions, 1 deletions

diff --git a/Doc/c-api/complex.rst b/Doc/c-api/complex.rst
index 675bd01..06dbb25 100644
--- a/Doc/c-api/complex.rst
+++ b/Doc/c-api/complex.rst
@@ -129,4 +129,10 @@ Complex Numbers as Python Objects
 
    If *op* is not a Python complex number object but has a :meth:`__complex__`
    method, this method will first be called to convert *op* to a Python complex
-   number object. Upon failure, this method returns ``-1.0`` as a real value.
+   number object.  If ``__complex__()`` is not defined then it falls back to
+   :meth:`__float__`.  If ``__float__()`` is not defined then it falls back
+   to :meth:`__index__`.  Upon failure, this method returns ``-1.0`` as a real
+   value.
+
+   .. versionchanged:: 3.8
+      Use :meth:`__index__` if available.
diff --git a/Doc/c-api/float.rst b/Doc/c-api/float.rst
index 8a99642..057ff52 100644
--- a/Doc/c-api/float.rst
+++ b/Doc/c-api/float.rst
@@ -47,9 +47,13 @@ Floating Point Objects
    Return a C :c:type:`double` representation of the contents of *pyfloat*.  If
    *pyfloat* is not a Python floating point object but has a :meth:`__float__`
    method, this method will first be called to convert *pyfloat* into a float.
+   If ``__float__()`` is not defined then it falls back to :meth:`__index__`.
    This method returns ``-1.0`` upon failure, so one should call
    :c:func:`PyErr_Occurred` to check for errors.
 
+   .. versionchanged:: 3.8
+      Use :meth:`__index__` if available.
+
 
 .. c:function:: double PyFloat_AS_DOUBLE(PyObject *pyfloat)