gh-144270: make SubElement parent and tag positional-only by NekoAsakura · Pull Request #144845 · python/cpython · GitHub

Make parent and tag positional-only in xml.etree.ElementTree.SubElement to match the C accelerator.

The C implementation (_elementtree.SubElement) uses PyArg_ParseTuple, which inherently makes parent and tag positional-only. The Python fallback used def SubElement(parent, tag, attrib={}, **extra): which allowed parent and tag as keyword arguments. This inconsistency meant SubElement(parent=e, tag="x") worked only when the C accelerator was unavailable.

Fix: add / after tag → def SubElement(parent, tag, /, attrib={}, **extra):

Changes

Lib/xml/etree/ElementTree.py: add / to SubElement signature
Lib/test/test_xml_etree.py: add test_subelement covering positional-only enforcement, keyword attrib, and kwargs-as-XML-attributes parity
Doc/library/xml.etree.elementtree.rst: update signature and add versionchanged:: 3.15

Note

Element.__init__ has the same Python/C signature mismatch — tag is positional-only in the C version (PyArg_ParseTuple at _elementtree.c:419) but accepts keywords in the Python
fallback (ElementTree.py:167). I will create a separate issue for that to keep this PR focused.

cpython/Lib/xml/etree/ElementTree.py

Line 167 in 23c488d

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

cpython/Modules/_elementtree.c

Lines 419 to 420 in 23c488d

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

Issue: xml.etree.ElementTree.SubElement definition is incorrect / inconsistent with C #144270

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LGTM. 👍

You could also merge two PRs in one.

The C accelerator implementations use PyArg_ParseTuple, which inherently enforces positional-only parameters. The Python fallback allowed these as keyword arguments, creating a behavioral mismatch. Make the tag parameter of Element.__init__ and the parent and tag parameters of SubElement positional-only to align with the C accelerator.

You could also merge two PRs in one.

Great. I've squashed the Element change from #144876 into this PR, you can close that one.

…element-positional-only

Merged. Thank you for your contribution, @NekoAsakura.

…ktor * upstream/main: (119 commits) pythongh-144270: Make SubElement parent and tag positional-only (pythonGH-144845) pythongh-146558: JIT optimize dict access for objects with known hash (python#146559) pythongh-139922: always run MSVC 64-bit tail-calling CI (pythonGH-146570) pythongh-126835: Fix _PY_IS_SMALL_INT() macro (python#146631) pythongh-146587: fix type slot assignment incase of multiple slots for same name (python#146593) pythongh-138122: Add differential flame graph (python#145785) pythongh-146416: Emscripten: Improve standard stream handling in node_entry.mjs (python#146417) pythongh-146444: Don't package as part of iOS 'build hosts' target (python#146628) pythongh-138850: Add --disable-epoll to configure (pythonGH-145768) pythongh-146444: Make Platforms/Apple/ compatible with Python 3.9 (python#146624) pythongh-138577: Fix keyboard shortcuts in getpass with echo_char (python#141597) pythongh-146556: Fix infinite loop in annotationlib.get_annotations() on circular __wrapped__ (python#146557) pythongh-146579: _zstd: Fix decompression options dict error message (python#146577) pythongh-146083: Upgrade bundled Expat to 2.7.5 (python#146085) pythongh-146080: fix a crash in SNI callbacks when the SSL object is gone (python#146573) pythongh-146090: fix memory management of internal `sqlite3` callback contexts (python#146569) pythongh-145876: Do not mask KeyErrors raised during dictionary unpacking in call (pythonGH-146472) pythongh-146004: fix test_args_from_interpreter_flags on windows (python#146580) pythongh-139003: Use frozenset for module level attributes in _pyrepl.utils (python#139004) pythonGH-146527: Add more data to GC statistics and add it to PyDebugOffsets (python#146532) ...

…onGH-144845) The C accelerator implementations use PyArg_ParseTuple, which inherently enforces positional-only parameters. The Python fallback allowed these as keyword arguments, creating a behavioral mismatch. Make the tag parameter of Element.__init__ and the parent and tag parameters of SubElement positional-only to align with the C accelerator.

bedevere-app Bot mentioned this pull request Feb 15, 2026

xml.etree.ElementTree.SubElement definition is incorrect / inconsistent with C #144270

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bedevere-app Bot added the awaiting review label Feb 15, 2026

NekoAsakura mentioned this pull request Feb 16, 2026

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

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NekoAsakura force-pushed the gh-144270-subelement-positional-only branch from d956c30 to 1551ff7 Compare February 16, 2026 15:41

brijkapadia reviewed Feb 16, 2026

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Comment thread Lib/test/test_xml_etree.py

serhiy-storchaka approved these changes Feb 19, 2026

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Comment thread Doc/library/xml.etree.elementtree.rst

Comment thread Lib/test/test_xml_etree.py

bedevere-app Bot added awaiting merge and removed awaiting review labels Feb 19, 2026

NekoAsakura force-pushed the gh-144270-subelement-positional-only branch from b9cacad to 38af9cf Compare February 19, 2026 21:46

Merge remote-tracking branch 'upstream/main' into pythongh-144270 -sub…

6f43dc8

…element-positional-only

serhiy-storchaka approved these changes Mar 30, 2026

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serhiy-storchaka merged commit afd8113 into python:main Mar 30, 2026
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bedevere-app Bot removed the awaiting merge label Mar 30, 2026

NekoAsakura deleted the gh-144270-subelement-positional-only branch March 30, 2026 16:42

pablogsal mentioned this pull request Apr 4, 2026

gh-130273: Fix traceback color output with unicode characters #142529

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gh-144270: make SubElement parent and tag positional-only by NekoAsakura · Pull Request #144845 · python/cpython · GitHub

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

gh-144270: make SubElement parent and tag positional-only by NekoAsakura · Pull Request #144845 · python/cpython · GitHub

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gh-144270: make SubElement parent and tag positional-only#144845
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NekoAsakura:gh-144270-subelement-positional-only

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