BUG: Raise TypeError only if key DataFrame is not empty #10195

Author: rekcahpassyla

pandas/core/frame.py

@@ -2151,7 +2151,7 @@ def _setitem_array(self, key, value):
     def _setitem_frame(self, key, value):
         # support boolean setting with DataFrame input, e.g.
         # df[df > df2] = 0
-        if key.values.dtype != np.bool_:
+        if key.values.size and key.values.dtype != np.bool_:
             raise TypeError('Must pass DataFrame with boolean values only')
 
         self._check_inplace_setting(value)

pandas/tests/test_frame.py

@@ -794,6 +794,24 @@ def test_setitem_empty(self):
         result.loc[result.b.isnull(), 'a'] = result.a
         assert_frame_equal(result, df)
 
+    def test_setitem_empty_frame_with_boolean(self):
+        # 
+        df = pd.DataFrame([[2, 2]], index=pd.DatetimeIndex(['2011-01-01']))
+        df2 = pd.DataFrame([[1, 1]], index=pd.DatetimeIndex(['2011-01-01']))
+
+        df[df > df2] = 47
+
+        assert np.all(df.values==47)
+
+        for dtype in ('float', 'int64'):
+            for df in [
+                    pd.DataFrame(dtype=dtype),
+                    pd.DataFrame(dtype=dtype, index=[1]),
+                    pd.DataFrame(dtype=dtype, columns=['A']),
+            ]:        
+                df2 = df.copy()
+                df[df > df2] = 47
+
     def test_delitem_corner(self):
         f = self.frame.copy()
         del f['D']