gh-150942: Speed up ElementTree attribute parsing

Author: deadlovelll

Misc/NEWS.d/next/Library/2026-06-09-23-04-44.gh-issue-150942.Iu583J.rst

@@ -0,0 +1,2 @@
+Speed up :mod:`xml.etree.ElementTree` parsing of element attributes by using
+reference-stealing dict insertion.

Modules/_elementtree.c

@@ -3343,9 +3343,7 @@ expat_start_handler(void *op, const XML_Char *tag_in,
                 Py_DECREF(tag);
                 return;
             }
-            ok = PyDict_SetItem(attrib, key, value);
-            Py_DECREF(value);
-            Py_DECREF(key);
+            ok = _PyDict_SetItem_Take2((PyDictObject *)attrib, key, value);
             if (ok < 0) {
                 Py_DECREF(attrib);
                 Py_DECREF(tag);