`Element.__init__` tag parameter has positional-only inconsistency

[NekoAsakura]

Bug report

Bug description:

Element.__init__ has the same Python/C signature inconsistency as SubElement (gh-144270).

Python fallback:

cpython/Lib/xml/etree/ElementTree.py

Line 167 in 23c488d

def __init__(self, tag, attrib={}, **extra):

tag accepts keyword arguments: Element(tag="foo") works.

C accelerator:

cpython/Modules/_elementtree.c

Lines 419 to 420 in 23c488d

	if (!PyArg_ParseTuple(args, "O|O!:Element", &tag, &PyDict_Type, &attrib))
	return -1;

PyArg_ParseTuple only parses positional args, so tag is positional-only. Element(tag="foo") raises TypeError.

Proposed fix

-    def __init__(self, tag, attrib={}, **extra):
+    def __init__(self, tag, /, attrib={}, **extra):

Same pattern as the SubElement fix in gh-144270.

Reproduce

import sys, importlib
import xml.etree.ElementTree as ET

root = ET.Element("root")

try:
    ET.Element(tag="foo")
except TypeError:
    print("C rejects Element(tag=...)")

sys.modules['_elementtree'] = None
importlib.reload(ET)

e = ET.Element(tag="foo")
print(f"pure-python accepted it: {e.tag}") 

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-144846: make Element tag positional-only #144876

[brijkapadia]

@NekoAsakura Do you want to create a PR or could I work on it?

[NekoAsakura]

Hi @bkap123 , cheers for the shout! I've already got the fix ready to go. I’ll whip a PR up now.