BUG: Fix for TypeError: unorderable types" for multi index (#15457)

Author: dickreuter

pandas/core/arrays/categorical.py

@@ -2538,7 +2538,10 @@ def _factorize_from_iterable(values):
                                       ordered=values.ordered)
         codes = values.codes
     else:
-        cat = Categorical(values, ordered=True)
+        # The value of ordered is irrelevant since we don't use cat as such,
+        # but only the resulting categories, the order of which is independent
+        # from ordered. Set ordered to False as default due to issue #15457
+        cat = Categorical(values, ordered=False)
         categories = cat.categories
         codes = cat.codes
     return codes, categories

pandas/tests/indexes/multi/test_constructor.py

@@ -313,6 +313,13 @@ def test_from_product_empty_zero_levels():
         MultiIndex.from_product([])
 
 
+def test_set_index_tuple():
+    # test for fix of issue #15457, where the following raised a TypeError
+    result = pd.MultiIndex.from_arrays([[2, 4], [1, (1, 2)]])
+    expected = pd.MultiIndex.from_tuples([(2, 4), (1, (1, 2))])
+    assert result == expected
+
+
 def test_from_product_empty_one_level():
     result = MultiIndex.from_product([[]], names=['A'])
     expected = pd.Index([], name='A')