Bug in loc raised Error when non-integer slice was given for MultiIndex

doc/source/whatsnew/v1.2.0.rst

@@ -469,6 +469,7 @@ 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` raised ``TypeError`` when non integer interval was given to select values from :class:`MultiIndex` (:issue:`25165`, :issue:`24263`)
 
 Missing
 ^^^^^^^

pandas/core/indexes/multi.py

@@ -2676,10 +2676,15 @@ 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:
+                start = idx.start
+                end = idx.stop
+            elif k < n - 1:
                 end = start + section.searchsorted(idx, side="right")
                 start = start + section.searchsorted(idx, side="left")
             else:
+                if isinstance(idx, slice):
+                    idx = idx.start
                 return start + section.searchsorted(idx, side=side)
 
     def _get_loc_single_level_index(self, level_index: Index, key: Hashable) -> int:
@@ -3048,22 +3053,25 @@ 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/indexing/multiindex/test_loc.py

@@ -623,3 +623,10 @@ 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: 18185
+    index = pd.date_range("2001-01-01", periods=100)
+    mi = MultiIndex.from_arrays([index])
+    assert mi.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 +215,30 @@ def test_setitem_multiple_partial(self, multiindex_dataframe_random_data):
         expected.loc["bar"] = 0
         tm.assert_series_equal(result, expected)
 
+    def test_partial_getitem_loc_datetime(self):
+        # 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(
+            [2, 3],
+            index=MultiIndex.from_product(
+                [[to_datetime("2019-02-01")], [0, 1]], names=["x", "y"]
+            ),
+        )
+        result = df["2019-2":]
+        tm.assert_frame_equal(result, expected)
+        result = df.loc["2019-2":]
+        tm.assert_frame_equal(result, expected)
+
+        result = df.loc(axis=0)["2019-2":]
+        tm.assert_frame_equal(result, expected)
+
+        result = df.loc["2019-2":, :]
+        tm.assert_frame_equal(result, expected)
+
 
 def test_loc_getitem_partial_both_axis():
     # gh-12660