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Fix astype(category) for empty column scenarios #21741

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Merged
mroeschke merged 1 commit into from
Mar 10, 2026
Merged

Fix astype(category) for empty column scenarios #21741

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6 changes: 3 additions & 3 deletions python/cudf/cudf/core/column/column.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2290,12 +2290,12 @@ def cast(self, dtype: DtypeObj) -> ColumnBase:
def astype(self, dtype: DtypeObj, copy: bool | None = False) -> ColumnBase:
if self.dtype == dtype:
result = self
elif isinstance(dtype, CategoricalDtype):
result = self.as_categorical_column(dtype)
elif len(self) == 0:
result = column_empty(0, dtype=dtype)
else:
if isinstance(dtype, CategoricalDtype):
result = self.as_categorical_column(dtype)
elif is_dtype_obj_interval(dtype):
if is_dtype_obj_interval(dtype):
result = self.as_interval_column(dtype) # type: ignore[arg-type]
elif is_dtype_obj_list(dtype) or is_dtype_obj_struct(dtype):
if isinstance(dtype, pd.ArrowDtype):
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7 changes: 6 additions & 1 deletion python/cudf/cudf/tests/series/methods/test_astype.py
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Expand Up @@ -145,7 +145,12 @@ def test_cast_float_nan_to_bool_pandas_compat():
def test_empty_astype_always_castable(type1, type2, as_dtype, copy):
ser = cudf.Series([], dtype=as_dtype(type1))
result = ser.astype(as_dtype(type2), copy=copy)
expected = cudf.Series([], dtype=as_dtype(type2))
if type2 == "category":
# Empty astype to category inherits the source dtype as the
# categories dtype, matching pandas behavior.
expected = cudf.Series([], dtype=result.dtype)
else:
expected = cudf.Series([], dtype=as_dtype(type2))
assert_eq(result, expected)
if not copy and cudf.dtype(type1) == cudf.dtype(type2):
assert ser._column is result._column
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