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Fix regression for loc and __setitem__ when one-dimensional tuple was given for MultiIndex #37787

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Merged
merged 8 commits into from
Nov 14, 2020
Merged

Fix regression for loc and __setitem__ when one-dimensional tuple was given for MultiIndex #37787

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8ccfd5a
Fix regression for loc and __setitem__ when one-dimensional tuple was…
phofl Nov 12, 2020
8113cf4
Use fixture to parametrize test
phofl Nov 12, 2020
5944255
Move whatsnew and remove pass
phofl Nov 13, 2020
3ac69ff
Merge branch 'master' of https://github.com/pandas-dev/pandas into 37711
phofl Nov 13, 2020
e3f90be
Add new test
phofl Nov 13, 2020
2f8c6ed
Run black
phofl Nov 13, 2020
cc15da3
FIx typo
phofl Nov 14, 2020
f8c86f5
Merge branch 'master' of https://github.com/pandas-dev/pandas into 37711
phofl Nov 14, 2020
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.2.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -470,6 +470,7 @@ Indexing
- Bug in :meth:`Index.where` incorrectly casting numeric values to strings (:issue:`37591`)
- Bug in :meth:`Series.loc` and :meth:`DataFrame.loc` raises when numeric label was given for object :class:`Index` although label was in :class:`Index` (:issue:`26491`)
- Bug in :meth:`DataFrame.loc` returned requested key plus missing values when ``loc`` was applied to single level from :class:`MultiIndex` (:issue:`27104`)
- Fixed regression in :meth:`DataFrame.loc` and :meth:`Series.loc` for ``__setitem__`` when one-dimensional tuple was given to select from :class:`MultiIndex` (:issue:`37711`)

Missing
^^^^^^^
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5 changes: 3 additions & 2 deletions pandas/core/indexing.py
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Expand Up @@ -650,11 +650,12 @@ def _ensure_listlike_indexer(self, key, axis=None, value=None):
if self.ndim != 2:
return

if isinstance(key, tuple):
if isinstance(key, tuple) and not isinstance(self.obj.index, ABCMultiIndex):
# key may be a tuple if we are .loc
# in that case, set key to the column part of key
# if index is not a MultiIndex, set key to column part
key = key[column_axis]
axis = column_axis
pass

if (
axis == column_axis
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14 changes: 14 additions & 0 deletions pandas/tests/indexing/multiindex/test_loc.py
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Expand Up @@ -288,6 +288,20 @@ def convert_nested_indexer(indexer_type, keys):

tm.assert_series_equal(result, expected)

def test_multiindex_loc_one_dimensional_tuple(self):
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use frame_or_series

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Done

# GH#37711
mi = MultiIndex.from_tuples([("a", "A"), ("b", "A")])
ser = Series([1, 2], index=mi)
df = ser.to_frame()

ser.loc[("a",)] = 0
expected = Series([0, 2], index=mi)
tm.assert_series_equal(ser, expected)

df.loc[("a",)] = 0
expected = expected.to_frame()
tm.assert_frame_equal(df, expected)


@pytest.mark.parametrize(
"indexer, pos",
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