gh-141460: make RLock a class instead of a factory function by chaope · Pull Request #142977 · python/cpython

chaope · 2025-12-19T12:26:35Z

gh-141460 make RLock a class instead of a factory function

📚 Documentation preview 📚: https://cpython-previews--142977.org.readthedocs.build/

…t_thread_module_has_signatures

Misc/NEWS.d/next/Library/2025-12-16-14-46-14.gh-issue-141460._44DYc.rst

…44DYc.rst Co-authored-by: AN Long <aisk@users.noreply.github.com>

vstinner

LGTM. It makes sense to remove the Python implementation and declare threading.RLock as a class.

vstinner · 2026-01-08T10:51:37Z

Misc/NEWS.d/next/Library/2025-12-16-14-46-14.gh-issue-141460._44DYc.rst

@@ -0,0 +1 @@
+Make :class:`threading.RLock` a real class instead of a factory function.


Please mention also that the Python implementation has been removed.

aisk · 2026-01-08T11:04:23Z

Lib/test/test_threading.py

-@unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C')
-class CRLockTests(lock_tests.RLockTests):
-    locktype = staticmethod(threading._CRLock)
+class RLockTests(lock_tests.RLockTests):


According to PEP 8, there should be two blank lines between classes. Other parts of this file may not follow PEP 8, but since we touched this part, let's update it (and keep the rest as it is).

Suggested change

class RLockTests(lock_tests.RLockTests):

class RLockTests(lock_tests.RLockTests):

kumaraditya303 · 2026-01-10T06:46:26Z

_thread.Lock is not a basetype, however _thread.RLock is a basetype. Given that previously this was a factory function and not intended for inheritance I think we should make _thread.RLock non-basetype.

picnixz · 2026-01-10T19:08:18Z

Lib/threading.py

-        return _PyRLock()
-    return _CRLock()
-
-class _RLock:


For backwards compatibility with people using threading._RLock for their types, could we keep _RLock = RLock? It doesn't cost us much and won't be an issue but at least it won't be cause breakage downstream where people assume _RLock to be a class.

Same with keeping _CRLock and _PyRLock just for backward compatibility.

I know that we don't need to do it, but it's preferrable that we don't remove symbols like that sitting for the past decades.

A code search on PyPI top 15,000 projects for threading._RLock found 6 matching projects:

PYPI-2026-01-07/astroid-4.0.3.tar.gz: astroid-4.0.3/tests/brain/test_multiprocessing.py: rlock_name = "threading._RLock" PYPI-2026-01-07/django_sendgrid_v5-1.3.1.tar.gz: django_sendgrid_v5-1.3.1/sendgrid_backend/mail.py: self._lock = None # type: Optional[threading._RLock] PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/gevent/threading.py: # Previously it was a factory function around threading._RLock PYPI-2026-01-07/prefect-3.6.9.tar.gz: prefect-3.6.9/src/prefect/_internal/concurrency/cancellation.py: self._lock = threading._RLock() # type: ignore # yes, we want the private version PYPI-2026-01-07/prefect_client-3.6.9.tar.gz: prefect_client-3.6.9/src/prefect/_internal/concurrency/cancellation.py: self._lock = threading._RLock() # type: ignore # yes, we want the private version PYPI-2026-01-07/pylint-4.0.4.tar.gz: pylint-4.0.4/pylint/checkers/refactoring/refactoring_checker.py: "threading._RLock.acquire",

I also found 7 projects embedding a copy of typeshed annotations (multiprocessing/managers.pyi) which also refers to threading._RLock. Example:

PYPI-2026-01-07/mypy-1.19.1.tar.gz: mypy-1.19.1/mypy/typeshed/stdlib/multiprocessing/managers.pyi: def Condition(self, lock: threading.Lock | threading._RLock | None = None) -> threading.Condition: ...

A code search on PyPI top 15,000 projects for threading._(CRLock|PyRLock) found 2 matching projects: eventlet and gevent.

PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/eventlet/patcher.py: threading.RLock = threading._PyRLock PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/eventlet/patcher.py: new = threading._PyRLock() PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/tests/isolated/patcher_existing_locks_preexisting.py: python_lock = threading._PyRLock PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/tests/isolated/patcher_existing_logging_module_lock.py: assert not isinstance(logging._lock, threading._PyRLock) PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/tests/isolated/patcher_existing_logging_module_lock.py: assert not isinstance(handler.lock, threading._PyRLock) PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/tests/isolated/patcher_existing_logging_module_lock.py: assert isinstance(logging._lock, threading._PyRLock) PYPI-2026-01-07/eventlet-0.40.4.tar.gz: eventlet-0.40.4/tests/isolated/patcher_existing_logging_module_lock.py: assert isinstance(handler.lock, threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/gevent/threading.py: # threading._CRLock, which is imported from _thread.RLock and as such PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.10/test_threading.py: locktype = staticmethod(threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.10/test_threading.py: @unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C') PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.10/test_threading.py: locktype = staticmethod(threading._CRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.11/test_threading.py: locktype = staticmethod(threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.11/test_threading.py: @unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C') PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.11/test_threading.py: locktype = staticmethod(threading._CRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.12/test_threading.py: locktype = staticmethod(threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.12/test_threading.py: @unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C') PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.12/test_threading.py: locktype = staticmethod(threading._CRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.13/test_threading.py: locktype = staticmethod(threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.13/test_threading.py: @unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C') PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.13/test_threading.py: locktype = staticmethod(threading._CRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.14/test_threading.py: locktype = staticmethod(threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.14/test_threading.py: @unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C') PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.14/test_threading.py: locktype = staticmethod(threading._CRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.9/test_threading.py: locktype = staticmethod(threading._PyRLock) PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.9/test_threading.py: @unittest.skipIf(threading._CRLock is None, 'RLock not implemented in C') PYPI-2026-01-07/gevent-25.9.1.tar.gz: gevent-25.9.1/src/greentest/3.9/test_threading.py: locktype = staticmethod(threading._CRLock)

Would it be possible to deprecate threading._RLock if we decide to keep it?

For _CRLock and _PyRLock, I don't think that we need to keep them. Impacted projects (eventlet, gevent) should be updated anyway for this change.

So, I think we need to contact those projects or make the change louder. This typically requires something in the What's New page. However, there might be other private projects that could be broken. I really don't want to remove this class like that. However, making the attribute raise a deprecation warning could be better. Yes, it will pollute outputs but people know that the implementation will really be different (that is, it will be using the C implementation).

picnixz · 2026-01-10T19:09:51Z

Lib/threading.py

-    __enter__ = acquire
-
-    def release(self):
-        """Release a lock, decrementing the recursion level.


Can you quickly check that the docstrings match the C docstrings as well please?

vstinner · 2026-01-12T13:00:47Z

_thread.Lock is not a basetype, however _thread.RLock is a basetype. Given that previously this was a factory function and not intended for inheritance I think we should make _thread.RLock non-basetype.

Oh, it's a good idea to remove the Py_TPFLAGS_BASETYPE flag.

chaope added 2 commits December 17, 2025 01:40

fix issue 141460

a73b47f

exclude RLock from test_threading_module_has_signatures following tes…

fb5d60b

…t_thread_module_has_signatures

bedevere-app bot mentioned this pull request Dec 19, 2025

Change RLock from factory function to actual type, remove dead Python RLock implementation #141460

Open

chaope marked this pull request as ready for review December 19, 2025 15:13

bedevere-app bot added the awaiting review label Dec 19, 2025

Merge branch 'main' into fix-issue-141460

f264156

aisk changed the title ~~gh-141460 make RLock a class instead of a factory function~~ gh-141460: make RLock a class instead of a factory function Dec 19, 2025

aisk reviewed Dec 19, 2025

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gh-141460: make RLock a class instead of a factory function#142977

gh-141460: make RLock a class instead of a factory function#142977
chaope wants to merge 4 commits intopython:mainfrom
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		@@ -0,0 +1 @@
		Make :class:`threading.RLock` a real class instead of a factory function.

	class RLockTests(lock_tests.RLockTests):

	class RLockTests(lock_tests.RLockTests):

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