FIX-modin-project#4354: Fix df.loc on multiindex dataframe

Signed-off-by: Naren Krishna <[email protected]>

modin/pandas/indexing.py

@@ -623,6 +623,10 @@ def __getitem__(self, key):
         """
         if self.df.empty:
             return self.df._default_to_pandas(lambda df: df.loc[key])
+        if isinstance(key, tuple):
+            loc_series = _LocIndexer(self.__getitem__(key[0])).__getitem__(key[1])
+            loc_series.name = (key[0], key[1])
+            return loc_series
         row_loc, col_loc, ndim = self._parse_row_and_column_locators(key)
         self.row_scalar = is_scalar(row_loc)
         self.col_scalar = is_scalar(col_loc)

modin/pandas/test/dataframe/test_indexing.py

@@ -664,6 +664,17 @@ def test_iloc_assignment():
     df_equals(modin_df, pandas_df)
 
 
+def test_loc_multiple_arguments():
+    arrays = [
+        np.array(["bar", "bar", "baz", "baz", "foo", "foo", "qux", "qux"]),
+        np.array(["one", "two", "one", "two", "one", "two", "one", "two"]),
+    ]
+    values = np.random.randn(8, 4)
+    modin_df = pd.DataFrame(values, index=arrays)
+    pandas_df = pandas.DataFrame(values, index=arrays)
+    df_equals(modin_df.loc['bar', 'one'], pandas_df.loc['bar', 'one'])
+
+
 @pytest.mark.parametrize("data", test_data_values, ids=test_data_keys)
 def test_iloc_nested_assignment(data):
     modin_df = pd.DataFrame(data)