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BUG: astype('category') on dataframe backed by non-writeable arrays raises ValueError #53678

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Merged
merged 1 commit into from
Jun 20, 2023
Merged

BUG: astype('category') on dataframe backed by non-writeable arrays raises ValueError #53678

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v2.1.0.rst
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Expand Up @@ -341,6 +341,7 @@ Bug fixes

Categorical
^^^^^^^^^^^
- Bug in :meth:`Series.astype` with ``dtype="category"`` for nullable arrays with read-only null value masks (:issue:`53658`)
- Bug in :meth:`Series.map` , where the value of the ``na_action`` parameter was not used if the series held a :class:`Categorical` (:issue:`22527`).
-

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2 changes: 1 addition & 1 deletion pandas/_libs/hashtable_class_helper.pxi.in
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Expand Up @@ -648,7 +648,7 @@ cdef class {{name}}HashTable(HashTable):
UInt8Vector result_mask
UInt8VectorData *rmd
bint use_na_value, use_mask, seen_na = False
uint8_t[:] mask_values
const uint8_t[:] mask_values

if return_inverse:
labels = np.empty(n, dtype=np.intp)
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9 changes: 9 additions & 0 deletions pandas/tests/extension/test_categorical.py
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Expand Up @@ -319,3 +319,12 @@ def test_repr_2d(self, data):

res = repr(data.reshape(-1, 1))
assert res.count("\nCategories") == 1


def test_astype_category_readonly_mask_values():
# GH 53658
df = pd.DataFrame([0, 1, 2], dtype="Int64")
df._mgr.arrays[0]._mask.flags["WRITEABLE"] = False
result = df.astype("category")
expected = pd.DataFrame([0, 1, 2], dtype="Int64").astype("category")
tm.assert_frame_equal(result, expected)