grant list.index() a more informative error message #7252
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 39b8b1a..dea51ed 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2276,7 +2276,8 @@
listindex(PyListObject *self, PyObject *args)
{
Py_ssize_t i, start=0, stop=Py_SIZE(self);
- PyObject *v;
+ PyObject *v, *format_tuple, *err_string;
+ static PyObject *err_format = NULL;
if (!PyArg_ParseTuple(args, "O|O&O&:index", &v,
_PyEval_SliceIndex, &start,
@@ -2299,7 +2300,20 @@
else if (cmp < 0)
return NULL;
}
- PyErr_SetString(PyExc_ValueError, "list.index(x): x not in list");
+ if (err_format == NULL) {
+ err_format = PyString_FromString("%r is not in list");
+ if (err_format == NULL)
+ return NULL;
+ }
+ format_tuple = PyTuple_Pack(1, v);
+ if (format_tuple == NULL)
+ return NULL;
+ err_string = PyString_Format(err_format, format_tuple);
+ Py_DECREF(format_tuple);
+ if (err_string == NULL)
+ return NULL;
+ PyErr_SetObject(PyExc_ValueError, err_string);
+ Py_DECREF(err_string);
return NULL;
}