bpo-35664: Optimize operator.itemgetter (GH-11435)
diff --git a/Lib/test/test_operator.py b/Lib/test/test_operator.py
index 6254091..f46d94a 100644
--- a/Lib/test/test_operator.py
+++ b/Lib/test/test_operator.py
@@ -401,6 +401,19 @@
self.assertEqual(operator.itemgetter(2,10,5)(data), ('2', '10', '5'))
self.assertRaises(TypeError, operator.itemgetter(2, 'x', 5), data)
+ # interesting indices
+ t = tuple('abcde')
+ self.assertEqual(operator.itemgetter(-1)(t), 'e')
+ self.assertEqual(operator.itemgetter(slice(2, 4))(t), ('c', 'd'))
+
+ # interesting sequences
+ class T(tuple):
+ 'Tuple subclass'
+ pass
+ self.assertEqual(operator.itemgetter(0)(T('abc')), 'a')
+ self.assertEqual(operator.itemgetter(0)(['a', 'b', 'c']), 'a')
+ self.assertEqual(operator.itemgetter(0)(range(100, 200)), 100)
+
def test_methodcaller(self):
operator = self.module
self.assertRaises(TypeError, operator.methodcaller)
diff --git a/Misc/NEWS.d/next/Library/2019-01-04-22-18-25.bpo-35664.Z-Gyyj.rst b/Misc/NEWS.d/next/Library/2019-01-04-22-18-25.bpo-35664.Z-Gyyj.rst
new file mode 100644
index 0000000..f4acc5a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-01-04-22-18-25.bpo-35664.Z-Gyyj.rst
@@ -0,0 +1,4 @@
+Improve operator.itemgetter() performance by 33% with optimized argument
+handling and with adding a fast path for the common case of a single
+non-negative integer index into a tuple (which is the typical use case in
+the standard library).
diff --git a/Modules/_operator.c b/Modules/_operator.c
index 3bf8c12..d6c6a18 100644
--- a/Modules/_operator.c
+++ b/Modules/_operator.c
@@ -937,6 +937,7 @@
PyObject_HEAD
Py_ssize_t nitems;
PyObject *item;
+ Py_ssize_t index; // -1 unless *item* is a single non-negative integer index
} itemgetterobject;
static PyTypeObject itemgetter_type;
@@ -948,6 +949,7 @@
itemgetterobject *ig;
PyObject *item;
Py_ssize_t nitems;
+ Py_ssize_t index;
if (!_PyArg_NoKeywords("itemgetter", kwds))
return NULL;
@@ -967,6 +969,21 @@
Py_INCREF(item);
ig->item = item;
ig->nitems = nitems;
+ ig->index = -1;
+ if (PyLong_CheckExact(item)) {
+ index = PyLong_AsSsize_t(item);
+ if (index < 0) {
+ /* If we get here, then either the index conversion failed
+ * due to being out of range, or the index was a negative
+ * integer. Either way, we clear any possible exception
+ * and fall back to the slow path, where ig->index is -1.
+ */
+ PyErr_Clear();
+ }
+ else {
+ ig->index = index;
+ }
+ }
PyObject_GC_Track(ig);
return (PyObject *)ig;
@@ -993,12 +1010,27 @@
PyObject *obj, *result;
Py_ssize_t i, nitems=ig->nitems;
- if (!_PyArg_NoKeywords("itemgetter", kw))
- return NULL;
- if (!PyArg_UnpackTuple(args, "itemgetter", 1, 1, &obj))
- return NULL;
- if (nitems == 1)
+ assert(PyTuple_CheckExact(args));
+ if (kw == NULL && PyTuple_GET_SIZE(args) == 1) {
+ obj = PyTuple_GET_ITEM(args, 0);
+ }
+ else {
+ if (!_PyArg_NoKeywords("itemgetter", kw))
+ return NULL;
+ if (!PyArg_UnpackTuple(args, "itemgetter", 1, 1, &obj))
+ return NULL;
+ }
+ if (nitems == 1) {
+ if (ig->index >= 0
+ && PyTuple_CheckExact(obj)
+ && ig->index < PyTuple_GET_SIZE(obj))
+ {
+ result = PyTuple_GET_ITEM(obj, ig->index);
+ Py_INCREF(result);
+ return result;
+ }
return PyObject_GetItem(obj, ig->item);
+ }
assert(PyTuple_Check(ig->item));
assert(PyTuple_GET_SIZE(ig->item) == nitems);