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BUG: Added manual checks for self-nested sequences during array creation #29623

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BUG: Added manual checks for self-nested sequences during array creation #29623

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fb89d44
BUG: added checks for cyclic self-nested sequences
devmt04 Aug 25, 2025
6f95e67
TST: modify tests for self-nested sequences
devmt04 Aug 25, 2025
349fd87
Merge branch 'numpy:main' into bugfix-29620-sequence-circular-recursion
devmt04 Aug 25, 2025
28834b1
BUG: added checks for self-nested sequences
devmt04 Aug 25, 2025
488bc88
TST: modify tests for self-nested sequences
devmt04 Aug 25, 2025
9706e6f
BUG: added checks for self-nested sequences
devmt04 Aug 25, 2025
d2c83a7
TST: modify tests for self-nested sequences
devmt04 Aug 25, 2025
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11 changes: 11 additions & 0 deletions numpy/_core/src/multiarray/array_coercion.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1197,6 +1197,17 @@ PyArray_DiscoverDTypeAndShape_Recursive(
copy = -1;
}

/* Check for self-nested sequences to prevent RAM exhaustion */
if (is_sequence) {
if (PySequence_Check(objects[0])) {
if (objects[0] == obj) {
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@jorenham jorenham Aug 25, 2025 •
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this still leaves

l = [[]]
l[0].append(l)
l[0].append(l)
np.array(l)

and 62 other cases like these

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(not that that's necessarily a problem, it's just something to be aware of)

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Yeah, I got u, this addresses only one specific and most common case of self-nesting. Thanks !

PyErr_SetString(PyExc_ValueError,
"NumPy array cannot be created using self-nested sequences.");
return -1;
}
}
}

/* Recursive call for each sequence item */
for (Py_ssize_t i = 0; i < size; i++) {
max_dims = PyArray_DiscoverDTypeAndShape_Recursive(
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11 changes: 7 additions & 4 deletions numpy/_core/tests/test_array_coercion.py
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Expand Up @@ -505,12 +505,15 @@ def test_pathological_self_containing(self):
# Test that this also works for two nested sequences
l = []
l.append(l)
arr = np.array([l, l, l], dtype=object)
assert arr.shape == (3,) + (1,) * (ncu.MAXDIMS - 1)

with pytest.raises(ValueError, match="cannot be created using self-nested"):
arr = np.array([l, l, l], dtype=object)
# assert arr.shape == (3,) + (1,) * (ncu.MAXDIMS - 1)

# Also check a ragged case:
arr = np.array([l, [None], l], dtype=object)
assert arr.shape == (3, 1)
with pytest.raises(ValueError, match="cannot be created using self-nested"):
arr = np.array([l, [None], l], dtype=object)
# assert arr.shape == (3, 1)

@pytest.mark.parametrize("arraylike", arraylikes())
def test_nested_arraylikes(self, arraylike):
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