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Make MultiIndex.get_loc raise for unhashable type #35914

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Merged
merged 2 commits into from
Sep 5, 2020
Merged

Make MultiIndex.get_loc raise for unhashable type #35914

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c190c76
Make MultiIndex.get_loc raise for unhashable type
dsaxton Aug 27, 2020
197ba93
Merge branch 'master' into get_loc-unhashable-argument
jreback Sep 5, 2020
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.1.2.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ Fixed regressions
~~~~~~~~~~~~~~~~~
- Regression in :meth:`DatetimeIndex.intersection` incorrectly raising ``AssertionError`` when intersecting against a list (:issue:`35876`)
- Performance regression for :meth:`RangeIndex.format` (:issue:`35712`)
- Regression where :meth:`MultiIndex.get_loc` would return a slice spanning the full index when passed an empty list (:issue:`35878`)
-


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5 changes: 3 additions & 2 deletions pandas/core/indexes/multi.py
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Expand Up @@ -2707,6 +2707,8 @@ def get_loc(self, key, method=None):
"currently supported for MultiIndex"
)

hash(key)
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should this raise InvalidIndexError?

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That was my original thought, but it broke an existing test because evidently passing a singleton list with only np.nan raises the unhashable type error (it hits a line that uses this approach of trying to hash the key):

import numpy as np
import pandas as pd

idx = pd.MultiIndex.from_tuples([("a", 1), ("b", 2)])
idx.get_loc([np.nan])
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-40dd73c454ae> in <module>
----> 1 idx.get_loc([np.nan])

~/opt/miniconda3/envs/pandas-1.1.1/lib/python3.8/site-packages/pandas/core/indexes/multi.py in get_loc(self, key, method)
   2717         lead_key, follow_key = key[:i], key[i:]
   2718         start, stop = (
-> 2719             self.slice_locs(lead_key, lead_key) if lead_key else (0, len(self))
   2720         )
   2721

~/opt/miniconda3/envs/pandas-1.1.1/lib/python3.8/site-packages/pandas/core/indexes/multi.py in slice_locs(self, start, end, step, kind)
   2578         # This function adds nothing to its parent implementation (the magic
   2579         # happens in get_slice_bound method), but it adds meaningful doc.
-> 2580         return super().slice_locs(start, end, step, kind=kind)
   2581
   2582     def _partial_tup_index(self, tup, side="left"):

~/opt/miniconda3/envs/pandas-1.1.1/lib/python3.8/site-packages/pandas/core/indexes/base.py in slice_locs(self, start, end, step, kind)
   5159         start_slice = None
   5160         if start is not None:
-> 5161             start_slice = self.get_slice_bound(start, "left", kind)
   5162         if start_slice is None:
   5163             start_slice = 0

~/opt/miniconda3/envs/pandas-1.1.1/lib/python3.8/site-packages/pandas/core/indexes/multi.py in get_slice_bound(self, label, side, kind)
   2522         if not isinstance(label, tuple):
   2523             label = (label,)
-> 2524         return self._partial_tup_index(label, side=side)
   2525
   2526     def slice_locs(self, start=None, end=None, step=None, kind=None):

~/opt/miniconda3/envs/pandas-1.1.1/lib/python3.8/site-packages/pandas/core/indexes/multi.py in _partial_tup_index(self, tup, side)
   2593             section = labs[start:end]
   2594
-> 2595             if lab not in lev and not isna(lab):
   2596                 if not lev.is_type_compatible(lib.infer_dtype([lab], skipna=False)):
   2597                     raise TypeError(f"Level type mismatch: {lab}")

~/opt/miniconda3/envs/pandas-1.1.1/lib/python3.8/site-packages/pandas/core/indexes/base.py in __contains__(self, key)
   4063         False
   4064         """
-> 4065         hash(key)
   4066         try:
   4067             return key in self._engine

TypeError: unhashable type: 'list'


def _maybe_to_slice(loc):
"""convert integer indexer to boolean mask or slice if possible"""
if not isinstance(loc, np.ndarray) or loc.dtype != "int64":
Expand All @@ -2721,8 +2723,7 @@ def _maybe_to_slice(loc):
mask[loc] = True
return mask

if not isinstance(key, (tuple, list)):
# not including list here breaks some indexing, xref #30892
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I think it is okay to remove this comment since we're not actually checking for list here, or should it be moved? cc @jbrockmendel

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i think youre right (though havent checked 30892)

if not isinstance(key, tuple):
loc = self._get_level_indexer(key, level=0)
return _maybe_to_slice(loc)

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2 changes: 1 addition & 1 deletion pandas/tests/frame/indexing/test_indexing.py
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Expand Up @@ -2111,7 +2111,7 @@ def test_type_error_multiindex(self):
)
dg = df.pivot_table(index="i", columns="c", values=["x", "y"])

with pytest.raises(TypeError, match="is an invalid key"):
with pytest.raises(TypeError, match="unhashable type"):
dg[:, 0]

index = Index(range(2), name="i")
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8 changes: 8 additions & 0 deletions pandas/tests/indexing/multiindex/test_multiindex.py
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@@ -1,4 +1,5 @@
import numpy as np
import pytest

import pandas._libs.index as _index
from pandas.errors import PerformanceWarning
Expand Down Expand Up @@ -83,3 +84,10 @@ def test_nested_tuples_duplicates(self):
df3 = df.copy(deep=True)
df3.loc[[(dti[0], "a")], "c2"] = 1.0
tm.assert_frame_equal(df3, expected)

def test_multiindex_get_loc_list_raises(self):
# https://github.com/pandas-dev/pandas/issues/35878
idx = pd.MultiIndex.from_tuples([("a", 1), ("b", 2)])
msg = "unhashable type"
with pytest.raises(TypeError, match=msg):
idx.get_loc([])
11 changes: 10 additions & 1 deletion pandas/tests/series/indexing/test_setitem.py
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@@ -1,6 +1,7 @@
import numpy as np

from pandas import NaT, Series, date_range
from pandas import MultiIndex, NaT, Series, date_range
import pandas.testing as tm


class TestSetitemDT64Values:
Expand All @@ -17,3 +18,11 @@ def test_setitem_none_nan(self):

series[5:7] = np.nan
assert series[6] is NaT

def test_setitem_multiindex_empty_slice(self):
# https://github.com/pandas-dev/pandas/issues/35878
idx = MultiIndex.from_tuples([("a", 1), ("b", 2)])
result = Series([1, 2], index=idx)
expected = result.copy()
result.loc[[]] = 0
tm.assert_series_equal(result, expected)