Mar 22, 2026 · Mar 22, 2026
diff --git a/Doc/c-api/file.rst b/Doc/c-api/file.rst

   Write object *obj* to file object *p*.  The only supported flag for *flags* is
   :c:macro:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
   instead of the :func:`repr`.  Return ``0`` on success or ``-1`` on failure; the
   appropriate exception will be set.
   instead of the :func:`repr`.

   If *obj* is ``NULL``, write the string ``"<NULL>"``.

   Return ``0`` on success or ``-1`` on failure; the
   appropriate exception will be set.

 .. c:function:: int PyFile_WriteString(const char *s, PyObject *p)

diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
   representation on success, ``NULL`` on failure.  This is the equivalent of the
   Python expression ``repr(o)``.  Called by the :func:`repr` built-in function.

   If argument is ``NULL``, return the string ``'<NULL>'``.

   .. versionchanged:: 3.4
      This function now includes a debug assertion to help ensure that it
      does not silently discard an active exception.
   a string similar to that returned by :c:func:`PyObject_Repr` in Python 2.
   Called by the :func:`ascii` built-in function.

   If argument is ``NULL``, return the string ``'<NULL>'``.

   .. index:: string; PyObject_Str (C function)


   Python expression ``str(o)``.  Called by the :func:`str` built-in function
   and, therefore, by the :func:`print` function.

   If argument is ``NULL``, return the string ``'<NULL>'``.

   .. versionchanged:: 3.4
      This function now includes a debug assertion to help ensure that it
      does not silently discard an active exception.
   a TypeError is raised when *o* is an integer instead of a zero-initialized
   bytes object.

   If argument is ``NULL``, return the :class:`bytes` object ``b'<NULL>'``.


 .. c:function:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)

diff --git a/Lib/test/test_capi/test_list.py b/Lib/test/test_capi/test_list.py
 # CRASHES list_extend(NULL, [])
 # CRASHES list_extend([], NULL)

 deftest_uninitialized_list_repr(self):
 lst=_testlimitedcapi.list_new(3)
 self.assertEqual(repr(lst),'[<NULL>, <NULL>, <NULL>]')


 if__name__=="__main__":
 unittest.main()
diff --git a/Lib/test/test_capi/test_tuple.py b/Lib/test/test_capi/test_tuple.py
        self.assertRaises(SystemError, resize, [1, 2, 3], 0, False)
        self.assertRaises(SystemError, resize, NULL, 0, False)

    def test_uninitialized_tuple_repr(self):
        tup = _testlimitedcapi.tuple_new(3)
        self.assertEqual(repr(tup), '(<NULL>, <NULL>, <NULL>)')


 if __name__ == "__main__":
    unittest.main()
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-03-18-18-52-00.gh-issue-146056.r1tVSo.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-03-18-18-52-00.gh-issue-146056.r1tVSo.rst
 Fix:func:`repr` for lists containing ``NULL``\s.
diff --git a/Objects/listobject.c b/Objects/listobject.c
       so must refetch the list size on each iteration. */
    for (i = 0; i < Py_SIZE(v); ++i) {
        /* Hold a strong reference since repr(item) can mutate the list */
        item =Py_NewRef(v->ob_item[i]);
        item =Py_XNewRef(v->ob_item[i]);

        if (i > 0) {
            if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -123,9 +123,12 @@ the :mod:`io` APIs instead.

		Write object obj to file object p. The only supported flag for flags is
		:c:macro:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
		instead of the :func:`repr`. Return ``0`` on success or ``-1`` on failure; the
		appropriate exception will be set.
		instead of the :func:`repr`.

		If obj is ``NULL``, write the string ``"<NULL>"``.

		Return ``0`` on success or ``-1`` on failure; the
		appropriate exception will be set.

		.. c:function:: int PyFile_WriteString(const char s, PyObject p)

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -319,6 +319,8 @@ Object Protocol
		representation on success, ``NULL`` on failure. This is the equivalent of the
		Python expression ``repr(o)``. Called by the :func:`repr` built-in function.

		If argument is ``NULL``, return the string ``'<NULL>'``.

		.. versionchanged:: 3.4
		This function now includes a debug assertion to help ensure that it
		does not silently discard an active exception.
Expand All		@@ -333,6 +335,8 @@ Object Protocol
		a string similar to that returned by :c:func:`PyObject_Repr` in Python 2.
		Called by the :func:`ascii` built-in function.

		If argument is ``NULL``, return the string ``'<NULL>'``.

		.. index:: string; PyObject_Str (C function)


Expand All		@@ -343,6 +347,8 @@ Object Protocol
		Python expression ``str(o)``. Called by the :func:`str` built-in function
		and, therefore, by the :func:`print` function.

		If argument is ``NULL``, return the string ``'<NULL>'``.

		.. versionchanged:: 3.4
		This function now includes a debug assertion to help ensure that it
		does not silently discard an active exception.
Expand All		@@ -358,6 +364,8 @@ Object Protocol
		a TypeError is raised when o is an integer instead of a zero-initialized
		bytes object.

		If argument is ``NULL``, return the :class:`bytes` object ``b'<NULL>'``.


		.. c:function:: int PyObject_IsSubclass(PyObject derived, PyObject cls)

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -352,6 +352,10 @@ def test_list_extend(self):
		# CRASHES list_extend(NULL, [])
		# CRASHES list_extend([], NULL)

		deftest_uninitialized_list_repr(self):
		lst=_testlimitedcapi.list_new(3)
		self.assertEqual(repr(lst),'[<NULL>, <NULL>, <NULL>]')


		if__name__=="__main__":
		unittest.main()
Original file line number	Diff line number	Diff line change
Expand Up		@@ -257,5 +257,10 @@ def test__tuple_resize(self):
		self.assertRaises(SystemError, resize, [1, 2, 3], 0, False)
		self.assertRaises(SystemError, resize, NULL, 0, False)

		def test_uninitialized_tuple_repr(self):
		tup = _testlimitedcapi.tuple_new(3)
		self.assertEqual(repr(tup), '(<NULL>, <NULL>, <NULL>)')


		if __name__ == "__main__":
		unittest.main()
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fix:func:`repr` for lists containing ``NULL``\s.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -604,7 +604,7 @@ list_repr_impl(PyListObject *v)
		so must refetch the list size on each iteration. */
		for (i = 0; i < Py_SIZE(v); ++i) {
		/* Hold a strong reference since repr(item) can mutate the list */
		item =Py_NewRef(v->ob_item[i]);
		item =Py_XNewRef(v->ob_item[i]);

		if (i > 0) {
		if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0)
Expand Down