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Merged
vstinner merged 4 commits into from
Oct 10, 2025
Merged

gh-111489: Add PyTuple_FromArray() function #139691

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ce1b2ff
gh-111489: Add PyTuple_FromArray() function
vstinner Oct 7, 2025
b0fbeae
Add test on empty tuple
vstinner Oct 7, 2025
cc47b10
Address Serhiy's review
vstinner Oct 7, 2025
89f91fc
Use SystemError for negative size
vstinner Oct 7, 2025
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Address Serhiy's review
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@vstinner
vstinner committed Oct 7, 2025
commit cc47b1035a33549a0cedb01d0db999f650e915bb
6 changes: 4 additions & 2 deletions Doc/c-api/tuple.rst
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Expand Up @@ -42,8 +42,10 @@ Tuple Objects
Create a tuple of *size* items and copy references from *array* to the new
tuple.
Comment on lines +42 to +43

@serhiy-storchaka serhiy-storchaka Oct 7, 2025

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I would prefer to formulate this in words more similar to PyTuple_New() or PyTuple_Pack() ("Return a new tuple object of size ... "), but this is not so important.


* Return a new reference on success.
* Set an exception and return ``NULL`` on error.
*array* can be NULL if *size* is ``0``.

On success, return a new reference.
On error, set an exception and return ``NULL``.

.. versionadded:: next

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34 changes: 22 additions & 12 deletions Lib/test/test_capi/test_tuple.py
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Expand Up @@ -62,6 +62,28 @@ def test_tuple_new(self):
self.assertRaises(SystemError, tuple_new, PY_SSIZE_T_MIN)
self.assertRaises(MemoryError, tuple_new, PY_SSIZE_T_MAX)

def test_tuple_fromarray(self):
# Test PyTuple_FromArray()
tuple_fromarray = _testcapi.tuple_fromarray

tup = tuple([i] for i in range(5))
copy = tuple_fromarray(tup)
self.assertEqual(copy, tup)

tup = ()
copy = tuple_fromarray(tup)
self.assertIs(copy, tup)

@serhiy-storchaka serhiy-storchaka Oct 7, 2025

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Is not the empty tuple singleton a CPython implementation detail?

@vstinner vstinner Oct 7, 2025

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The whole file is a CPython implementation detail (_testcapi), no?


copy = tuple_fromarray(NULL, 0)
self.assertIs(copy, ())

with self.assertRaises(ValueError):
tuple_fromarray(NULL, -1)
with self.assertRaises(ValueError):
tuple_fromarray(NULL, PY_SSIZE_T_MIN)
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with self.assertRaises(MemoryError):
tuple_fromarray(NULL, PY_SSIZE_T_MAX)

def test_tuple_pack(self):
# Test PyTuple_Pack()
pack = _testlimitedcapi.tuple_pack
Expand Down Expand Up @@ -279,18 +301,6 @@ def my_iter():
self.assertEqual(tuple(my_iter()), (TAG, *range(10)))
self.assertEqual(tuples, [])

def test_tuple_fromarray(self):
# Test PyTuple_FromArray()
tuple_fromarray = _testcapi.tuple_fromarray

tup = tuple(object() for _ in range(5))
copy = tuple_fromarray(tup)
self.assertEqual(copy, tup)

tup = ()
copy = tuple_fromarray(tup)
self.assertIs(copy, tup)


if __name__ == "__main__":
unittest.main()
40 changes: 13 additions & 27 deletions Modules/_testcapi/tuple.c
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Expand Up @@ -108,40 +108,26 @@ static PyObject *
tuple_fromarray(PyObject* Py_UNUSED(module), PyObject *args)
{
PyObject *src;
if (!PyArg_ParseTuple(args, "O!", &PyTuple_Type, &src)) {
Py_ssize_t size = -1;
if (!PyArg_ParseTuple(args, "O|n", &src, &size)) {
return NULL;
}

Py_ssize_t size = PyTuple_GET_SIZE(src);
PyObject **array = PyMem_Malloc(size * sizeof(PyObject**));
if (array == NULL) {
PyErr_NoMemory();
if (src != Py_None && !PyTuple_Check(src)) {
PyErr_SetString(PyExc_TypeError, "expect a tuple");
return NULL;
}
for (Py_ssize_t i = 0; i < size; i++) {
array[i] = Py_NewRef(PyTuple_GET_ITEM(src, i));
}

PyObject *tuple = PyTuple_FromArray(array, size);
if (tuple == NULL) {
goto done;
}

for (Py_ssize_t i = 0; i < size; i++) {
// check that the array is not modified
assert(array[i] == PyTuple_GET_ITEM(src, i));

// check that the array was copied properly
assert(PyTuple_GET_ITEM(tuple, i) == array[i]);
PyObject **items;
if (src != Py_None) {
items = &PyTuple_GET_ITEM(src, 0);
if (size < 0) {
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size = PyTuple_GET_SIZE(src);
}
}

done:
for (Py_ssize_t i = 0; i < size; i++) {
Py_DECREF(array[i]);
else {
items = NULL;
}
PyMem_Free(array);

return tuple;
return PyTuple_FromArray(items, size);
}


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4 changes: 4 additions & 0 deletions Objects/tupleobject.c
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Expand Up @@ -371,6 +371,10 @@ PyTuple_FromArray(PyObject *const *src, Py_ssize_t n)
if (n == 0) {
return tuple_get_empty();
}
if (n < 0) {
PyErr_SetString(PyExc_ValueError, "size must be nonnegative");
return NULL;
}
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PyTupleObject *tuple = tuple_alloc(n);
if (tuple == NULL) {
Expand Down
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