Index: Objects/unicodeobject.c
===================================================================
--- Objects/unicodeobject.c	(revision 79048)
+++ Objects/unicodeobject.c	(working copy)
@@ -8666,6 +8666,7 @@
     {"isprintable", (PyCFunction) unicode_isprintable, METH_NOARGS, isprintable__doc__},
     {"zfill", (PyCFunction) unicode_zfill, METH_VARARGS, zfill__doc__},
     {"format", (PyCFunction) do_string_format, METH_VARARGS | METH_KEYWORDS, format__doc__},
+    {"format_using_mapping", (PyCFunction) do_string_format_using_mapping, METH_O, format__doc__},
     {"__format__", (PyCFunction) unicode__format__, METH_VARARGS, p_format__doc__},
     {"_formatter_field_name_split", (PyCFunction) formatter_field_name_split, METH_NOARGS},
     {"_formatter_parser", (PyCFunction) formatter_parser, METH_NOARGS},
Index: Objects/stringlib/string_format.h
===================================================================
--- Objects/stringlib/string_format.h	(revision 79048)
+++ Objects/stringlib/string_format.h	(working copy)
@@ -495,7 +495,11 @@
         PyObject *key = SubString_new_object(&first);
         if (key == NULL)
             goto error;
-        if ((kwargs == NULL) || (obj = PyDict_GetItem(kwargs, key)) == NULL) {
+
+        /* Use PyObject_GetItem instead of PyDict_GetItem because this
+           code is no longer just used with kwargs. It might be passed
+           a non-dict when called through format_using_mapping. */
+        if ((kwargs == NULL) || (obj = PyObject_GetItem(kwargs, key)) == NULL) {
             PyErr_SetObject(PyExc_KeyError, key);
             Py_DECREF(key);
             goto error;
@@ -1035,6 +1039,11 @@
     return build_string(&input, args, kwargs, recursion_depth, &auto_number);
 }
 
+static PyObject *
+do_string_format_using_mapping(PyObject *self, PyObject *obj)
+{
+    return do_string_format(self, NULL, obj);
+}
 
 
 /************************************************************************/