Checking in the code for PEP 357.

This was mostly written by Travis Oliphant.
I've inspected it all; Neal Norwitz and MvL have also looked at it
(in an earlier incarnation).

1 files changed, 38 insertions, 0 deletions

diff --git a/Objects/classobject.c b/Objects/classobject.c
index 34afb9e..037252d 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -1733,6 +1733,43 @@ instance_nonzero(PyInstanceObject *self)
 	return outcome > 0;
 }
 
+static Py_ssize_t
+instance_index(PyInstanceObject *self)
+{
+	PyObject *func, *res;
+	Py_ssize_t outcome;
+	static PyObject *indexstr = NULL;
+
+	if (indexstr == NULL) {
+		indexstr = PyString_InternFromString("__index__");
+		if (indexstr == NULL)
+			return -1;
+	}	
+	if ((func = instance_getattr(self, indexstr)) == NULL) {
+		if (!PyErr_ExceptionMatches(PyExc_AttributeError))
+			return -1;
+		PyErr_Clear();
+		PyErr_SetString(PyExc_TypeError, 
+				"object cannot be interpreted as an index");
+		return -1;
+	}
+	res = PyEval_CallObject(func, (PyObject *)NULL);
+	Py_DECREF(func);
+	if (res == NULL)
+		return -1;
+	if (PyInt_Check(res) || PyLong_Check(res)) {
+		outcome = res->ob_type->tp_as_number->nb_index(res);
+	}
+	else {
+		PyErr_SetString(PyExc_TypeError, 
+				"__index__ must return an int or a long");
+		outcome = -1;
+	}
+	Py_DECREF(res);
+	return outcome;
+}
+
+
 UNARY(instance_invert, "__invert__")
 UNARY(instance_int, "__int__")
 UNARY(instance_long, "__long__")
@@ -2052,6 +2089,7 @@ static PyNumberMethods instance_as_number = {
 	(binaryfunc)instance_truediv,		/* nb_true_divide */
 	(binaryfunc)instance_ifloordiv,		/* nb_inplace_floor_divide */
 	(binaryfunc)instance_itruediv,		/* nb_inplace_true_divide */
+	(lenfunc)instance_index,		/* nb_index */
 };
 
 PyTypeObject PyInstance_Type = {