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BUG: Count creates result with read_only array #51943

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Merged
merged 2 commits into from
Mar 14, 2023
Merged

BUG: Count creates result with read_only array #51943

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9424073
BUG: Count creates result with read_only array
phofl Mar 13, 2023
692f68e
Merge branch 'main' into cow_count_read_only_array
phofl Mar 13, 2023
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2 changes: 1 addition & 1 deletion pandas/core/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10870,7 +10870,7 @@ def count(self, axis: Axis = 0, numeric_only: bool = False):
else:
# GH13407
series_counts = notna(frame).sum(axis=axis)
counts = series_counts.values
counts = series_counts._values
result = self._constructor_sliced(
counts, index=frame._get_agg_axis(axis)
)
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8 changes: 8 additions & 0 deletions pandas/tests/copy_view/test_methods.py
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Expand Up @@ -1674,6 +1674,14 @@ def test_transpose_ea_single_column(using_copy_on_write):
assert not np.shares_memory(get_array(df, "a"), get_array(result, 0))


def test_count_read_only_array():
df = DataFrame({"a": [1, 2], "b": 3})
result = df.count()
result.iloc[0] = 100
expected = Series([100, 2], index=["a", "b"])
tm.assert_series_equal(result, expected)


def test_series_view(using_copy_on_write):
ser = Series([1, 2, 3])
ser_orig = ser.copy()
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