gh-144846: make Element tag positional-only

Doc/library/xml.etree.elementtree.rst

@@ -879,7 +879,7 @@ Element Objects
    :noindex:
    :no-index:
 
-.. class:: Element(tag, attrib={}, **extra)
+.. class:: Element(tag, /, attrib={}, **extra)
 
    Element class.  This class defines the Element interface, and provides a
    reference implementation of this interface.
@@ -889,6 +889,9 @@ Element Objects
    an optional dictionary, containing element attributes.  *extra* contains
    additional attributes, given as keyword arguments.
 
+   .. versionchanged:: 3.15
+      *tag* is now a positional-only parameter.
+
 
    .. attribute:: tag
 

Lib/test/test_xml_etree.py

@@ -381,6 +381,22 @@ def test_simpleops(self):
         self.serialize_check(element,
                 '<tag key="value"><subtag /><subtag /></tag>')
 
+    def test_positional_only_parameter(self):
+        # Test Element positional-only parameters (gh-144846).
+
+        # 'tag' is positional-only
+        with self.assertRaises(TypeError):
+            ET.Element(tag='fail')
+
+        # 'attrib' can be passed as keyword
+        e = ET.Element('e', attrib={'key': 'value'})
+        self.assertEqual(e.get('key'), 'value')
+
+        # 'tag' as kwarg becomes an XML attribute, not the element tag
+        e = ET.Element('e', tag='foo')
+        self.assertEqual(e.tag, 'e')
+        self.assertEqual(e.get('tag'), 'foo')
+
     def test_cdata(self):
         # Test CDATA handling (etc).
 

Lib/xml/etree/ElementTree.py

@@ -164,7 +164,7 @@ class Element:
 
     """
 
-    def __init__(self, tag, attrib={}, **extra):
+    def __init__(self, tag, /, attrib={}, **extra):
         if not isinstance(attrib, dict):
             raise TypeError("attrib must be dict, not %s" % (
                 attrib.__class__.__name__,))

Misc/NEWS.d/next/Library/2026-02-16-10-32-44.gh-issue-144846.4eda4bd2.rst

@@ -0,0 +1,2 @@
+Made the *tag* parameter of :class:`xml.etree.ElementTree.Element`
+positional-only, matching the behavior of the C accelerator.