I propose to deprecate 42 private functions of the C API:

• _PyArg_ParseTupleAndKeywordsFast(): see [C API] Removed private _PyArg_Parser API has no replacement in Python 3.13 #112136
• _PyCode_CheckLineNumber()
• _PyDict_GetItem_KnownHash()
• _PyDict_NewPresized(): see [C API] Add PyDict_NewPresized() function #139772
• _PyErr_ChainExceptions1(): see _PyErr_ChainExceptions1 no longer avallable to extension modules in Python 3.13 alpha headers #116809
• _PyEval_SliceIndex()
• _PyEval_SliceIndexNotNone()
• _PyFrame_IsEntryFrame()
• _PyInterpreterState_GetEvalFrameFunc(), _PyInterpreterState_SetEvalFrameFunc(), _PyEval_EvalFrameDefault(): PEP 523, see [C API] Promote PEP 523 functions to public functions: add PyUnstable_InterpreterState_SetEvalFrameFunc() #141518
• _PyInterpreterState_RequireIDRef()
• _PyInterpreterState_RequiresIDRef()
• _PyLong_AsByteArray(): use PyLong_AsNativeBytes()
• _PyLong_Copy()
• _PyLong_FromByteArray(): use PyLong_FromNativeBytes()
• _PyLong_GCD(): call Python math.gcd() function
• _PyLong_NumBits(): call Python int.bit_length() method
• _PyObject_CallMethodId(): use PyObject_CallMethod()
• _PyObject_Dump(): see [C API] Promote _PyObject_Dump() to a public function #141070
• _PyObject_FunctionStr()
• _PyObject_GetAttrId(): use PyObject_GetAttr()
• _PyObject_GetDictPtr(): see [C API] Add PyObject_GetDict() function #139852
• _PySlice_FromIndices(): use PySlice_New()
• _PySlice_GetLongIndices()
• _PyStack_AsDict()
• _PyThread_CurrentFrames(): call Python sys._current_frames() function
• _PyType_Lookup(), _PyType_LookupRef(): see [C API] Add PyType_Lookup() function #139847
• _PyType_Name(): use PyType_GetName()
• _PyUnicode_FromId(): use PyUnicode_FromString() and cache the result; see the old discussion (2023)
• _PyWeakref_ClearRef()
• _Py_BreakPoint()
• _Py_GetGlobalRefTotal(), _Py_GetLegacyRefTotal(), _PyInterpreterState_GetRefTotal(): call Python sys.gettotalrefcount() function
• _Py_HashDouble(): see decision issue #2 and decision issue #10
• _Py_NewReference(), _Py_NewReferenceNoTotal(), _Py_ForgetReference(), _Py_ResurrectReference(): see old issue
• _Py_ReachedRecursionLimitWithMargin(): see gh-130396: Remove _Py_ReachedRecursionLimitWithMargin() function #141951

If one of these functions is used, users should request a public C API replacing the private function.

I propose to not schedule the removal of these functions for now.