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BUG: Series.at returning Series with one element instead of scalar #38101

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Merged
merged 4 commits into from
Nov 29, 2020
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Merged

BUG: Series.at returning Series with one element instead of scalar #38101

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4bdb7e9
Fix at bug
phofl Nov 25, 2020
ce8eb8d
Add test and whatsnew
phofl Nov 26, 2020
a6cf297
Refactor tests
phofl Nov 26, 2020
f887f6a
Fix bug
phofl Nov 28, 2020
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.2.0.rst
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Expand Up @@ -625,6 +625,7 @@ Indexing
- Bug in :meth:`DataFrame.iloc` and :meth:`Series.iloc` aligning objects in ``__setitem__`` (:issue:`22046`)
- Bug in :meth:`DataFrame.loc` did not raise ``KeyError`` when missing combination was given with ``slice(None)`` for remaining levels (:issue:`19556`)
- Bug in :meth:`DataFrame.loc` raising ``TypeError`` when non-integer slice was given to select values from :class:`MultiIndex` (:issue:`25165`, :issue:`24263`)
- Bug in :meth:`Series.at` returning :class:`Series` with one element instead of scalar (:issue:`38053`)
- Bug in :meth:`DataFrame.loc` returning and assigning elements in wrong order when indexer is differently ordered than the :class:`MultiIndex` to filter (:issue:`31330`, :issue:`34603`)
- Bug in :meth:`DataFrame.loc` and :meth:`DataFrame.__getitem__` raising ``KeyError`` when columns were :class:`MultiIndex` with only one level (:issue:`29749`)

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3 changes: 3 additions & 0 deletions pandas/core/indexes/multi.py
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Expand Up @@ -2527,6 +2527,9 @@ def _get_values_for_loc(self, series: "Series", loc, key):
if is_scalar(loc):
return new_values

if len(new_values) == 1:
return new_values[0]

new_index = self[loc]
new_index = maybe_droplevels(new_index, key)
new_ser = series._constructor(new_values, index=new_index, name=series.name)
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7 changes: 7 additions & 0 deletions pandas/tests/indexing/test_scalar.py
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Expand Up @@ -300,3 +300,10 @@ def test_multiindex_at_set():
assert series.at[1, 3] == 5
series.loc[1, 3] = 6
assert series.loc[1, 3] == 6


def test_at_get_multiindex_one_level():
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can you rename to
test_multiindex_at_get_one_level

do we have similar tests? can you co-locate

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In the same file above and test_at. One in test_partial, but this one is checking different things

Renamed the test

# GH#38053
s2 = Series((0, 1), index=[[False, True]])
result = s2.at[False]
assert result == 0