BUG: unstack fills True for boolean frame #1820

Author: changhiskhan

pandas/core/reshape.py

@@ -159,6 +159,8 @@ def get_new_values(self):
 
         if issubclass(values.dtype.type, np.integer):
             new_values = new_values.astype(float)
+        elif issubclass(values.dtype.type, np.bool_):
+            new_values = new_values.astype(object)
 
         new_values.fill(np.nan)
 
@@ -171,6 +173,7 @@ def get_new_values(self):
             mask_chunk.flat[self.mask] = True
 
         new_values = new_values.take(self.unique_groups, axis=0)
+
         return new_values, new_mask
 
     def get_new_columns(self):

pandas/tests/test_frame.py

@@ -6253,6 +6253,18 @@ def test_stack_unstack(self):
         assert_frame_equal(unstacked_cols.T, self.frame)
         assert_frame_equal(unstacked_cols_df['bar'].T, self.frame)
 
+    def test_unstack_bool(self):
+        df = DataFrame([False, False],
+                       index=MultiIndex.from_arrays([['a', 'b'], ['c', 'l']]),
+                       columns=['col'])
+        rs = df.unstack()
+        xp = DataFrame(np.array([[False, np.nan], [np.nan, False]],
+                                dtype=object),
+                       index=['a', 'b'],
+                       columns=MultiIndex.from_arrays([['col', 'col'],
+                                                       ['c', 'l']]))
+        assert_frame_equal(rs, xp)
+
     def test_unstack_to_series(self):
         # check reversibility
         data = self.frame.unstack()