Endow dict views with a proper length method.

Lib/test/test_dictviews.py

@@ -7,16 +7,19 @@ class DictSetTest(unittest.TestCase):
         d = {1: 10, "a": "ABC"}
         keys = d.KEYS()
         self.assertEqual(set(keys), {1, "a"})
+        self.assertEqual(len(keys), 2)
 
     def test_dict_items(self):
         d = {1: 10, "a": "ABC"}
         items = d.ITEMS()
         self.assertEqual(set(items), {(1, 10), ("a", "ABC")})
+        self.assertEqual(len(items), 2)
 
     def test_dict_values(self):
         d = {1: 10, "a": "ABC"}
         values = d.VALUES()
         self.assertEqual(set(values), {10, "ABC"})
+        self.assertEqual(len(values), 2)
 
 def test_main():
     test_support.run_unittest(DictSetTest)

Objects/dictobject.c

@@ -2354,13 +2354,13 @@ dictview_dealloc(dictviewobject *ds)
 	PyObject_Del(ds);
 }
 
-static PyObject *
+static Py_ssize_t
-dictview_length_hint(dictviewobject *ds)
+dictview_len(dictviewobject *ds)
 {
 	Py_ssize_t len = 0;
 	if (ds->ds_dict != NULL)
 		len = ds->ds_dict->ma_used;
-	return PyInt_FromSize_t(len);
+	return len;
 }
 
 static PyObject *
@@ -2397,9 +2397,18 @@ dictkeys_iter(dictviewobject *ds)
 	return dictiter_new(ds->ds_dict, &PyDictIterKey_Type);
 }
 
+static PySequenceMethods dictkeys_as_sequence = {
+	(lenfunc)dictview_len,		/* sq_length */
+	0,				/* sq_concat */
+	0,				/* sq_repeat */
+	0,				/* sq_item */
+	0,				/* sq_slice */
+	0,				/* sq_ass_item */
+	0,				/* sq_ass_slice */
+	(objobjproc)0,			/* sq_contains */
+};
+
 static PyMethodDef dictkeys_methods[] = {
-	{"__length_hint__", (PyCFunction)dictview_length_hint, METH_NOARGS,
-         length_hint_doc},
  	{NULL,		NULL}		/* sentinel */
 };
 
@@ -2417,7 +2426,7 @@ PyTypeObject PyDictKeys_Type = {
 	0,					/* tp_compare */
 	0,					/* tp_repr */
 	0,					/* tp_as_number */
-	0,					/* tp_as_sequence */
+	&dictkeys_as_sequence,			/* tp_as_sequence */
 	0,					/* tp_as_mapping */
 	0,					/* tp_hash */
 	0,					/* tp_call */
@@ -2454,9 +2463,18 @@ dictitems_iter(dictviewobject *ds)
 	return dictiter_new(ds->ds_dict, &PyDictIterItem_Type);
 }
 
+static PySequenceMethods dictitems_as_sequence = {
+	(lenfunc)dictview_len,		/* sq_length */
+	0,				/* sq_concat */
+	0,				/* sq_repeat */
+	0,				/* sq_item */
+	0,				/* sq_slice */
+	0,				/* sq_ass_item */
+	0,				/* sq_ass_slice */
+	(objobjproc)0,			/* sq_contains */
+};
+
 static PyMethodDef dictitems_methods[] = {
-	{"__length_hint__", (PyCFunction)dictview_length_hint, METH_NOARGS,
-         length_hint_doc},
  	{NULL,		NULL}		/* sentinel */
 };
 
@@ -2474,7 +2492,7 @@ PyTypeObject PyDictItems_Type = {
 	0,					/* tp_compare */
 	0,					/* tp_repr */
 	0,					/* tp_as_number */
-	0,					/* tp_as_sequence */
+	&dictitems_as_sequence,			/* tp_as_sequence */
 	0,					/* tp_as_mapping */
 	0,					/* tp_hash */
 	0,					/* tp_call */
@@ -2511,9 +2529,18 @@ dictvalues_iter(dictviewobject *ds)
 	return dictiter_new(ds->ds_dict, &PyDictIterValue_Type);
 }
 
+static PySequenceMethods dictvalues_as_sequence = {
+	(lenfunc)dictview_len,		/* sq_length */
+	0,				/* sq_concat */
+	0,				/* sq_repeat */
+	0,				/* sq_item */
+	0,				/* sq_slice */
+	0,				/* sq_ass_item */
+	0,				/* sq_ass_slice */
+	(objobjproc)0,			/* sq_contains */
+};
+
 static PyMethodDef dictvalues_methods[] = {
-	{"__length_hint__", (PyCFunction)dictview_length_hint, METH_NOARGS,
-         length_hint_doc},
  	{NULL,		NULL}		/* sentinel */
 };
 
@@ -2531,7 +2558,7 @@ PyTypeObject PyDictValues_Type = {
 	0,					/* tp_compare */
 	0,					/* tp_repr */
 	0,					/* tp_as_number */
-	0,					/* tp_as_sequence */
+	&dictvalues_as_sequence,		/* tp_as_sequence */
 	0,					/* tp_as_mapping */
 	0,					/* tp_hash */
 	0,					/* tp_call */