BUG: Index sortlevel ascending add type checking #32334

doc/source/whatsnew/v1.2.0.rst

@@ -352,7 +352,7 @@ Indexing
 - Bug in :meth:`PeriodIndex.get_loc` incorrectly raising ``ValueError`` on non-datelike strings instead of ``KeyError``, causing similar errors in :meth:`Series.__geitem__`, :meth:`Series.__contains__`, and :meth:`Series.loc.__getitem__` (:issue:`34240`)
 - Bug in :meth:`Index.sort_values` where, when empty values were passed, the method would break by trying to compare missing values instead of pushing them to the end of the sort order. (:issue:`35584`)
 - Bug in :meth:`Index.get_indexer` and :meth:`Index.get_indexer_non_unique` where int64 arrays are returned instead of intp. (:issue:`36359`)
--
+- Bug in :meth:`DataFrame.sort_index` where parameter ascending passed as a list on a single level index gives wrong result. (:issue:`32334`)
 
 Missing
 ^^^^^^^

pandas/core/indexes/base.py

@@ -1515,6 +1515,20 @@ def sortlevel(self, level=None, ascending=True, sort_remaining=None):
         -------
         Index
         """
+        if not isinstance(ascending, (list, bool)):
+            raise TypeError(
+                "ascending must be a single bool value or"
+                "a list of bool values of length 1"
+            )
+
+        if isinstance(ascending, list):
+            if len(ascending) != 1:
+                raise TypeError("ascending must be a list of bool values of length 1")
+            ascending = ascending[0]
+
+        if not isinstance(ascending, bool):
+            raise TypeError("ascending must be a bool value")
+
         return self.sort_values(return_indexer=True, ascending=ascending)
 
     def _get_level_values(self, level):

pandas/tests/indexes/test_base.py

@@ -2222,6 +2222,31 @@ def test_contains_method_removed(self, index):
             with pytest.raises(AttributeError, match=msg):
                 index.contains(1)
 
+    def test_sortlevel(self):
+        index = pd.Index([5, 4, 3, 2, 1])
+        with pytest.raises(Exception, match="ascending must be a single bool value or"):
+            index.sortlevel(ascending="True")
+
+        with pytest.raises(
+            Exception, match="ascending must be a list of bool values of length 1"
+        ):
+            index.sortlevel(ascending=[True, True])
+
+        with pytest.raises(Exception, match="ascending must be a bool value"):
+            index.sortlevel(ascending=["True"])
+
+        expected = pd.Index([1, 2, 3, 4, 5])
+        result = index.sortlevel(ascending=[True])
+        tm.assert_index_equal(result[0], expected)
+
+        expected = pd.Index([1, 2, 3, 4, 5])
+        result = index.sortlevel(ascending=True)
+        tm.assert_index_equal(result[0], expected)
+
+        expected = pd.Index([5, 4, 3, 2, 1])
+        result = index.sortlevel(ascending=False)
+        tm.assert_index_equal(result[0], expected)
+
 
 class TestMixedIntIndex(Base):
     # Mostly the tests from common.py for which the results differ