xml.etree.ElementTree.SubElement definition is incorrect / inconsistent with C

[Timmmm]

Bug report

Bug description:

This code runs fine on Python 3.13.7:

import xml.etree.ElementTree as ET
x = ET.Element("x")
ET.SubElement(x, 0, parent="0")

However, Pyright correctly detects a type error in the SubElement call. SubElement has this Python signature:

def SubElement(parent, tag, attrib={}, **extra):

The parent parameter has already been assigned, so this should fail. I believe the fact that it doesn't is because it's actually using a C implementation, and the C implementation has this type signature:

def SubElement(parent, tag, /, attrib={}, **extra):

Which does allow specifying parent="0".

So I think the solution is just to add that / into the Python code.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-144270: Fix xml.etree.ElementTree.SubElement signature inconsistency #144313
• gh-144270: make SubElement parent and tag positional-only #144845

[serhiy-storchaka]

@Timmmm, your idea looks good to me. Are you interesting in creating a PR?