Bug in loc raised Error when non-integer slice was given for MultiIndex (pandas-dev#37707)

Author: phofl

doc/source/whatsnew/v1.2.0.rst

@@ -620,6 +620,7 @@ Indexing
 - Bug in indexing on a :class:`Series` or :class:`DataFrame` with a :class:`CategoricalIndex` using listlike indexer that contains elements that are in the index's ``categories`` but not in the index itself failing to raise ``KeyError`` (:issue:`37901`)
 - 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`)
 
 Missing
 ^^^^^^^

pandas/core/indexes/multi.py

@@ -2764,9 +2764,17 @@ def _partial_tup_index(self, tup, side="left"):
                 return start + section.searchsorted(loc, side=side)
 
             idx = self._get_loc_single_level_index(lev, lab)
-            if k < n - 1:
+            if isinstance(idx, slice) and k < n - 1:
+                # Get start and end value from slice, necessary when a non-integer
+                # interval is given as input GH#37707
+                start = idx.start
+                end = idx.stop
+            elif k < n - 1:
                 end = start + section.searchsorted(idx, side="right")
                 start = start + section.searchsorted(idx, side="left")
+            elif isinstance(idx, slice):
+                idx = idx.start
+                return start + section.searchsorted(idx, side=side)
             else:
                 return start + section.searchsorted(idx, side=side)
 
@@ -3102,6 +3110,8 @@ def convert_indexer(start, stop, step, indexer=indexer, codes=level_codes):
                     start = 0
                 if key.stop is not None:
                     stop = level_index.get_loc(key.stop)
+                elif isinstance(start, slice):
+                    stop = len(level_index)
                 else:
                     stop = len(level_index) - 1
                 step = key.step
@@ -3136,22 +3146,27 @@ def convert_indexer(start, stop, step, indexer=indexer, codes=level_codes):
 
         else:
 
-            code = self._get_loc_single_level_index(level_index, key)
+            idx = self._get_loc_single_level_index(level_index, key)
 
             if level > 0 or self.lexsort_depth == 0:
                 # Desired level is not sorted
-                locs = np.array(level_codes == code, dtype=bool, copy=False)
+                locs = np.array(level_codes == idx, dtype=bool, copy=False)
                 if not locs.any():
                     # The label is present in self.levels[level] but unused:
                     raise KeyError(key)
                 return locs
 
-            i = level_codes.searchsorted(code, side="left")
-            j = level_codes.searchsorted(code, side="right")
-            if i == j:
+            if isinstance(idx, slice):
+                start = idx.start
+                end = idx.stop
+            else:
+                start = level_codes.searchsorted(idx, side="left")
+                end = level_codes.searchsorted(idx, side="right")
+
+            if start == end:
                 # The label is present in self.levels[level] but unused:
                 raise KeyError(key)
-            return slice(i, j)
+            return slice(start, end)
 
     def get_locs(self, seq):
         """

pandas/tests/indexes/multi/test_indexing.py

@@ -768,7 +768,7 @@ def test_timestamp_multiindex_indexer():
         [
             pd.date_range(
                 start="2019-01-02T00:15:33",
-                end="2019-01-05T02:15:33",
+                end="2019-01-05T03:15:33",
                 freq="H",
                 name="date",
             ),

pandas/tests/indexing/multiindex/test_loc.py

@@ -659,3 +659,12 @@ def test_getitem_non_found_tuple():
     )
     with pytest.raises(KeyError, match=r"\(2\.0, 2\.0, 3\.0\)"):
         df.loc[(2.0, 2.0, 3.0)]
+
+
+def test_get_loc_datetime_index():
+    # GH#24263
+    index = pd.date_range("2001-01-01", periods=100)
+    mi = MultiIndex.from_arrays([index])
+    # Check if get_loc matches for Index and MultiIndex
+    assert mi.get_loc("2001-01") == slice(0, 31, None)
+    assert index.get_loc("2001-01") == slice(0, 31, None)

pandas/tests/indexing/multiindex/test_partial.py

@@ -1,7 +1,14 @@
 import numpy as np
 import pytest
 
-from pandas import DataFrame, Float64Index, Int64Index, MultiIndex
+from pandas import (
+    DataFrame,
+    Float64Index,
+    Int64Index,
+    MultiIndex,
+    date_range,
+    to_datetime,
+)
 import pandas._testing as tm
 
 
@@ -208,6 +215,45 @@ def test_setitem_multiple_partial(self, multiindex_dataframe_random_data):
         expected.loc["bar"] = 0
         tm.assert_series_equal(result, expected)
 
+    @pytest.mark.parametrize(
+        "indexer, exp_idx, exp_values",
+        [
+            (slice("2019-2", None), [to_datetime("2019-02-01")], [2, 3]),
+            (
+                slice(None, "2019-2"),
+                date_range("2019", periods=2, freq="MS"),
+                [0, 1, 2, 3],
+            ),
+        ],
+    )
+    def test_partial_getitem_loc_datetime(self, indexer, exp_idx, exp_values):
+        # GH: 25165
+        date_idx = date_range("2019", periods=2, freq="MS")
+        df = DataFrame(
+            list(range(4)),
+            index=MultiIndex.from_product([date_idx, [0, 1]], names=["x", "y"]),
+        )
+        expected = DataFrame(
+            exp_values,
+            index=MultiIndex.from_product([exp_idx, [0, 1]], names=["x", "y"]),
+        )
+        result = df[indexer]
+        tm.assert_frame_equal(result, expected)
+        result = df.loc[indexer]
+        tm.assert_frame_equal(result, expected)
+
+        result = df.loc(axis=0)[indexer]
+        tm.assert_frame_equal(result, expected)
+
+        result = df.loc[indexer, :]
+        tm.assert_frame_equal(result, expected)
+
+        df2 = df.swaplevel(0, 1).sort_index()
+        expected = expected.swaplevel(0, 1).sort_index()
+
+        result = df2.loc[:, indexer, :]
+        tm.assert_frame_equal(result, expected)
+
 
 def test_loc_getitem_partial_both_axis():
     # gh-12660