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Bug in loc did not raise KeyError when missing combination with slice(None) was given #37764

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Merged
merged 9 commits into from
Nov 21, 2020
Merged

Bug in loc did not raise KeyError when missing combination with slice(None) was given #37764

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af28c7f
Bug in loc did not raise KeyError when missing combination with slice…
phofl Nov 11, 2020
5d68a7b
Fix pattern
phofl Nov 11, 2020
97368da
Raise in get_locs
phofl Nov 12, 2020
8e02be2
Add test
phofl Nov 13, 2020
5737da0
Merge branch 'master' of https://github.com/pandas-dev/pandas into 19556
phofl Nov 13, 2020
c74d0c6
Run black
phofl Nov 13, 2020
acd54af
Merge branch 'master' into 19556
jreback Nov 14, 2020
3e4919e
Merge branch 'master' of https://github.com/pandas-dev/pandas into 19556
phofl Nov 20, 2020
bdd4e5d
Merge branch '19556' of https://github.com/phofl/pandas into 19556
phofl Nov 20, 2020
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.2.0.rst
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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`)
- Bug in :meth:`DataFrame.loc` did not raise ``KeyError`` when missing combination was given with ``slice(None)`` for remaining levels (:issue:`19556`)

Missing
^^^^^^^
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2 changes: 2 additions & 0 deletions pandas/core/indexing.py
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Expand Up @@ -1107,6 +1107,8 @@ def _getitem_axis(self, key, axis: int):
# nested tuple slicing
if is_nested_tuple(key, labels):
locs = labels.get_locs(key)
if not len(locs):
raise KeyError(key)
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if this is going to raise (not 100% sure, but leaning towards yes), i think it should happen in MultiIndex.get_locs

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Could not find any information in the docs, if get_locs should raise when the combination of both keys is not found in MultiIndex. Would prefer that too, but did not want to break anything, hence my question above. Will try to introduce this there

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We are raising in get_locs now. This should be much more stable

indexer = [slice(None)] * self.ndim
indexer[axis] = locs
return self.obj.iloc[tuple(indexer)]
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14 changes: 14 additions & 0 deletions pandas/tests/indexing/multiindex/test_loc.py
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Expand Up @@ -591,6 +591,20 @@ def test_missing_key_raises_keyerror2(self):
with pytest.raises(KeyError, match=r"\(0, 3\)"):
ser.loc[0, 3]

def test_missing_key_combination(self):
# GH: 19556
mi = MultiIndex.from_arrays(
[
np.array(["a", "a", "b", "b"]),
np.array(["1", "2", "2", "3"]),
np.array(["c", "d", "c", "d"]),
],
names=["one", "two", "three"],
)
df = DataFrame(np.random.rand(4, 3), index=mi)
with pytest.raises(KeyError, match=r"\('b', '1', slice\(None, None, None\)\)"):
df.loc[("b", "1", slice(None)), :]


def test_getitem_loc_commutability(multiindex_year_month_day_dataframe_random_data):
df = multiindex_year_month_day_dataframe_random_data
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