BUG: unstack fails for mixed dtype subset

doc/source/v0.14.1.txt

@@ -235,3 +235,4 @@ Bug Fixes
 
 - Bug in non-monotonic ``Index.union`` may preserve ``name`` incorrectly (:issue:`7458`)
 - Bug in ``DatetimeIndex.intersection`` doesn't preserve timezone (:issue:`4690`)
+- Bug in ``unstack`` when columns contained mixed dtypes (:issue:`7405`).

pandas/core/reshape.py

@@ -242,7 +242,12 @@ def get_new_index(self):
 
         # construct the new index
         if len(self.new_index_levels) == 1:
+            result_labels = result_labels[0]
             new_index = self.new_index_levels[0]
+
+            if len(new_index) != len(result_labels):
+                new_index = new_index.take(result_labels)
+
             new_index.name = self.new_index_names[0]
         else:
             new_index = MultiIndex(levels=self.new_index_levels,

pandas/tests/test_frame.py

@@ -11706,6 +11706,38 @@ def test_unstack_non_unique_index_names(self):
         with tm.assertRaises(ValueError):
             df.T.stack('c1')
 
+    def test_unstack_mixed_dtypes(self):
+        n = 5
+        df = DataFrame({'A': ['a'] * n,
+                        'B': pd.date_range('20120101', periods=n),
+                        'C': np.zeros(n),
+                        'D': np.zeros(n, dtype='i8')}).set_index(list("AB"))
+        expected = df.unstack(0).iloc[:3]
+        result = df.iloc[:3].unstack(0)
+        tm.assert_frame_equal(result, expected)
+
+    def test_unstack_mixed_dtypes_different_method(self):
+        n = 5
+        df = DataFrame({'A': ['a'] * n,
+                        'B': pd.date_range('20120101', periods=n),
+                        'C': np.zeros(n),
+                        'D': np.zeros(n, dtype='i8')}).set_index(list("AB"))
+        result = df.iloc[:3].unstack(0)
+        other = df.iloc[:3].reset_index().set_index(list("AB")).unstack(0)
+        tm.assert_frame_equal(result, other)
+
+    def test_unstack_mixed_dtypes_with_mi_and_nat_different_method(self):
+        n = 5
+        B = pd.date_range('20120101', periods=n - 1).tolist()
+        B.insert(3, pd.NaT)
+        df = DataFrame({'A': ['a'] * n,
+                        'B': B,
+                        'C': np.zeros(n),
+                        'D': np.zeros(n, dtype='i8')}).set_index(list("AB"))
+        result = df.iloc[:3].unstack(0)
+        other = df.iloc[:3].reset_index().set_index(list("AB")).unstack(0)
+        tm.assert_frame_equal(result, other)
+
     def test_repr_with_mi_nat(self):
         df = DataFrame({'X': [1, 2]},
                        index=[[pd.NaT, pd.Timestamp('20130101')], ['a', 'b']])