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Backport PR #48324 on branch 1.5.x (BUG: Add note in whatsnew for DataFrame.at behavior change) #48345

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Merged
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Sep 1, 2022
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Backport PR #48324 on branch 1.5.x (BUG: Add note in whatsnew for DataFrame.at behavior change) #48345

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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v1.5.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1081,7 +1081,7 @@ Indexing
- Bug in :meth:`DataFrame.sum` min_count changes dtype if input contains NaNs (:issue:`46947`)
- Bug in :class:`IntervalTree` that lead to an infinite recursion. (:issue:`46658`)
- Bug in :class:`PeriodIndex` raising ``AttributeError`` when indexing on ``NA``, rather than putting ``NaT`` in its place. (:issue:`46673`)
-
- Bug in :meth:`DataFrame.at` would allow the modification of multiple columns (:issue:`48296`)

Missing
^^^^^^^
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8 changes: 8 additions & 0 deletions pandas/tests/indexing/test_at.py
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Expand Up @@ -6,6 +6,8 @@
import numpy as np
import pytest

from pandas.errors import InvalidIndexError

from pandas import (
CategoricalDtype,
CategoricalIndex,
Expand Down Expand Up @@ -192,6 +194,12 @@ def test_at_frame_raises_key_error2(self, indexer_al):
with pytest.raises(KeyError, match="^0$"):
indexer_al(df)["a", 0]

def test_at_frame_multiple_columns(self):
# GH#48296 - at shouldn't modify multiple columns
df = DataFrame({"a": [1, 2], "b": [3, 4]})
with pytest.raises(InvalidIndexError, match=r"slice\(None, None, None\)"):
df.at[5] = [6, 7]

def test_at_getitem_mixed_index_no_fallback(self):
# GH#19860
ser = Series([1, 2, 3, 4, 5], index=["a", "b", "c", 1, 2])
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