more tests; handle sorth with ordered

Author: chris-b1

pandas/tools/tests/test_concat.py

@@ -990,7 +990,7 @@ def test_union_categoricals_ordered(self):
             union_categoricals([c1, c2])
 
     def test_union_categoricals_sort(self):
-        # GH 13763
+        # GH 13846
         c1 = Categorical(['x', 'y', 'z'])
         c2 = Categorical(['a', 'b', 'c'])
         result = union_categoricals([c1, c2], sort_categories=True)
@@ -1033,6 +1033,63 @@ def test_union_categoricals_sort(self):
         expected = Categorical([])
         tm.assert_categorical_equal(result, expected)
 
+        c1 = Categorical(['b', 'a'], categories=['b', 'a', 'c'], ordered=True)
+        c2 = Categorical(['a', 'c'], categories=['b', 'a', 'c'], ordered=True)
+        with tm.assertRaises(TypeError):
+            union_categoricals([c1, c2], sort_categories=True)
+
+    def test_union_categoricals_sort_false(self):
+        # GH 13846
+        c1 = Categorical(['x', 'y', 'z'])
+        c2 = Categorical(['a', 'b', 'c'])
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical(['x', 'y', 'z', 'a', 'b', 'c'],
+                               categories=['x', 'y', 'z', 'a', 'b', 'c'])
+        tm.assert_categorical_equal(result, expected)
+
+        # fastpath
+        c1 = Categorical(['a', 'b'], categories=['b', 'a', 'c'])
+        c2 = Categorical(['b', 'c'], categories=['b', 'a', 'c'])
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical(['a', 'b', 'b', 'c'],
+                               categories=['b', 'a', 'c'])
+        tm.assert_categorical_equal(result, expected)
+
+        # fastpath - skip resort
+        c1 = Categorical(['a', 'b'], categories=['a', 'b', 'c'])
+        c2 = Categorical(['b', 'c'], categories=['a', 'b', 'c'])
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical(['a', 'b', 'b', 'c'],
+                               categories=['a', 'b', 'c'])
+        tm.assert_categorical_equal(result, expected)
+
+        c1 = Categorical(['x', np.nan])
+        c2 = Categorical([np.nan, 'b'])
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical(['x', np.nan, np.nan, 'b'],
+                               categories=['x', 'b'])
+        tm.assert_categorical_equal(result, expected)
+
+        c1 = Categorical([np.nan])
+        c2 = Categorical([np.nan])
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical([np.nan, np.nan], categories=[])
+        tm.assert_categorical_equal(result, expected)
+
+        c1 = Categorical([])
+        c2 = Categorical([])
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical([])
+        tm.assert_categorical_equal(result, expected)
+
+        c1 = Categorical(['b', 'a'], categories=['b', 'a', 'c'], ordered=True)
+        c2 = Categorical(['a', 'c'], categories=['b', 'a', 'c'], ordered=True)
+        result = union_categoricals([c1, c2], sort_categories=False)
+        expected = Categorical(['b', 'a', 'a', 'c'],
+                               categories=['b', 'a', 'c'], ordered=True)
+        tm.assert_categorical_equal(result, expected)
+
+
     def test_concat_bug_1719(self):
         ts1 = tm.makeTimeSeries()
         ts2 = tm.makeTimeSeries()[::2]

pandas/types/concat.py

@@ -223,7 +223,7 @@ def union_categoricals(to_union, sort_categories=False):
     to_union : list-like of Categoricals
     sort_categories : boolean, default False
         If true, resulting categories will be lexsorted, otherwise
-        they will be ordered as they appear in the data
+        they will be ordered as they appear in the data.
 
     Returns
     -------
@@ -235,6 +235,7 @@ def union_categoricals(to_union, sort_categories=False):
         - all inputs do not have the same dtype
         - all inputs do not have the same ordered property
         - all inputs are ordered and their categories are not identical
+        - sort_categories=True and Categoricals are ordered
     ValueError
         Emmpty list of categoricals passed
     """
@@ -256,6 +257,10 @@ def union_categoricals(to_union, sort_categories=False):
         ordered = first.ordered
         new_codes = np.concatenate([c.codes for c in to_union])
 
+        if sort_categories and ordered:
+            raise TypeError("Cannot use sort_categories=True with "
+                            "ordered Categoricals")
+
         if sort_categories and not categories.is_monotonic_increasing:
             categories = categories.sort_values()
             indexer = first.categories.get_indexer(categories)