Dec 27, 2022 · Jul 6, 2022 · Jul 6, 2022 · Jul 6, 2022 · Jul 8, 2022 · Jul 10, 2022
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-06-18-44-00.gh-issue-94603.Q_03xV.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-06-18-44-00.gh-issue-94603.Q_03xV.rst
 Improve performance of ``list.pop`` for small lists.
diff --git a/Objects/listobject.c b/Objects/listobject.c
        PyErr_SetString(PyExc_IndexError, "pop index out of range");
        return NULL;
    }
    v = self->ob_item[index];
 if (index == Py_SIZE(self) - 1) {
    status = list_resize(self, Py_SIZE(self) - 1);
    if (status >= 0)
        return v; /* and v now owns the reference the list had */
 else
    return NULL;

 PyObject **items =self->ob_item;
 v = items[index];
 const Py_ssize_t size_after_pop = Py_SIZE(self) - 1;
 if (size_after_pop == 0) {
 Py_INCREF(v);
 status = _list_clear(self);
    }
    Py_INCREF(v);
    status = list_ass_slice(self, index, index+1, (PyObject *)NULL);
    if (status < 0) {
        Py_DECREF(v);
    else {
        if ((size_after_pop - index) > 0) {
            memmove(&items[index], &items[index+1], (size_after_pop - index) * sizeof(PyObject *));
        }
        status = list_resize(self, size_after_pop);
    }
    if (status >= 0) {
        return v; // and v now owns the reference the list had
    }
    else {
        // list resize failed, need to restore
        memmove(&items[index+1], &items[index], (size_after_pop - index)* sizeof(PyObject *));
        items[index] = v;
        return NULL;
    }
    return v;
 }

 /* Reverse a slice of a list in place, from lo up to (exclusive) hi. */
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Improve performance of ``list.pop`` for small lists.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1022,21 +1022,29 @@ list_pop_impl(PyListObject *self, Py_ssize_t index)
		PyErr_SetString(PyExc_IndexError, "pop index out of range");
		return NULL;
		}
		v = self->ob_item[index];
		if (index == Py_SIZE(self) - 1) {
		status = list_resize(self, Py_SIZE(self) - 1);
		if (status >= 0)
		return v; /* and v now owns the reference the list had */
		else
		return NULL;

		PyObject **items =self->ob_item;
		v = items[index];
		const Py_ssize_t size_after_pop = Py_SIZE(self) - 1;
		if (size_after_pop == 0) {
		Py_INCREF(v);
		status = _list_clear(self);
		}
		Py_INCREF(v);
		status = list_ass_slice(self, index, index+1, (PyObject *)NULL);
		if (status < 0) {
		Py_DECREF(v);
		else {
		if ((size_after_pop - index) > 0) {
		memmove(&items[index], &items[index+1], (size_after_pop - index) * sizeof(PyObject *));
		}
		status = list_resize(self, size_after_pop);
		}
		if (status >= 0) {
		return v; // and v now owns the reference the list had
		}
		else {
		// list resize failed, need to restore
		memmove(&items[index+1], &items[index], (size_after_pop - index)* sizeof(PyObject *));
		items[index] = v;
		return NULL;
		}
		return v;
		}

		/* Reverse a slice of a list in place, from lo up to (exclusive) hi. */
Expand Down