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BUG: Setting values on DataFrame with multi-index .loc(axis=0) access adds columns #58301

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Merged
merged 5 commits into from
Apr 18, 2024
Merged

BUG: Setting values on DataFrame with multi-index .loc(axis=0) access adds columns #58301

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dc514fa
fixed the issue by making sure setting an item takes into account the…
eshaready Apr 17, 2024
86d7520
Merge branch 'pandas-dev:main' into multi-index-issue
eshaready Apr 17, 2024
18fecdd
Running pre commit checks
eshaready Apr 17, 2024
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eshaready Apr 17, 2024
00098ef
Update doc/source/whatsnew/v3.0.0.rst
eshaready Apr 18, 2024
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v3.0.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -397,7 +397,7 @@ Missing

MultiIndex
^^^^^^^^^^
-
- Bug in :func:`_LocationIndexer.__setitem__` where columns were added when they shouldn't be when using :func:`DataFrame.loc` with a multi index and specified axis (:issue:`58116`)
-

I/O
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8 changes: 5 additions & 3 deletions pandas/core/indexing.py
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Expand Up @@ -757,7 +757,7 @@ def _get_setitem_indexer(self, key):
"""
if self.name == "loc":
# always holds here bc iloc overrides _get_setitem_indexer
self._ensure_listlike_indexer(key)
self._ensure_listlike_indexer(key, axis=self.axis)

if isinstance(key, tuple):
for x in key:
Expand Down Expand Up @@ -857,8 +857,10 @@ def _ensure_listlike_indexer(self, key, axis=None, value=None) -> None:
if isinstance(key, tuple) and len(key) > 1:
# key may be a tuple if we are .loc
# if length of key is > 1 set key to column part
key = key[column_axis]
axis = column_axis
# unless axis is already specified, then go with that
if axis is None:
axis = column_axis
key = key[axis]

if (
axis == column_axis
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23 changes: 23 additions & 0 deletions pandas/tests/indexing/multiindex/test_loc.py
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Expand Up @@ -381,6 +381,29 @@ def test_multiindex_setitem_columns_enlarging(self, indexer, exp_value):
)
tm.assert_frame_equal(df, expected)

def test_multiindex_setitem_axis_set(self):
# GH#58116
dates = pd.date_range("2001-01-01", freq="D", periods=2)
ids = ["i1", "i2", "i3"]
index = MultiIndex.from_product([dates, ids], names=["date", "identifier"])
df = DataFrame(0.0, index=index, columns=["A", "B"])
df.loc(axis=0)["2001-01-01", ["i1", "i3"]] = None

expected = DataFrame(
[
[None, None],
[0.0, 0.0],
[None, None],
[0.0, 0.0],
[0.0, 0.0],
[0.0, 0.0],
],
index=index,
columns=["A", "B"],
)

tm.assert_frame_equal(df, expected)

def test_sorted_multiindex_after_union(self):
# GH#44752
midx = MultiIndex.from_product(
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