BUG: fix issue of boolean comparison on empty DataFrames (GH5808)

Author: jreback

doc/source/release.rst

@@ -74,6 +74,7 @@ Bug Fixes
   - Bug in Series replace with timestamp dict (:issue:`5797`)
   - read_csv/read_table now respects the `prefix` kwarg (:issue:`5732`).
   - Bug in selection with missing values via ``.ix`` from a duplicate indexed DataFrame failing (:issue:`5835`)
+  - Fix issue of boolean comparison on empty DataFrames (:issue:`5808`)
 
 pandas 0.13.0
 -------------

pandas/core/ops.py

@@ -736,11 +736,16 @@ def na_op(x, y):
                 result = np.empty(x.size, dtype=dtype)
                 yrav = y.ravel()
                 mask = notnull(xrav) & notnull(yrav)
-                result[mask] = op(xrav[mask], yrav[mask])
+                xrav = xrav[mask]
+                yrav = yrav[mask]
+                if np.prod(xrav.shape) and np.prod(yrav.shape):
+                    result[mask] = op(xrav, yrav)
             else:
                 result = np.empty(x.size, dtype=x.dtype)
                 mask = notnull(xrav)
-                result[mask] = op(xrav[mask], y)
+                xrav = xrav[mask]
+                if np.prod(xrav.shape):
+                    result[mask] = op(xrav, y)
 
             result, changed = com._maybe_upcast_putmask(result, -mask, np.nan)
             result = result.reshape(x.shape)

pandas/tests/test_frame.py

@@ -4392,6 +4392,41 @@ def test_operators(self):
         df = DataFrame({'a': ['a', None, 'b']})
         assert_frame_equal(df + df, DataFrame({'a': ['aa', np.nan, 'bb']}))
 
+    def test_operators_boolean(self):
+
+        # GH 5808
+        # empty frames, non-mixed dtype
+
+        result = DataFrame(index=[1]) & DataFrame(index=[1])
+        assert_frame_equal(result,DataFrame(index=[1]))
+
+        result = DataFrame(index=[1]) | DataFrame(index=[1])
+        assert_frame_equal(result,DataFrame(index=[1]))
+
+        result = DataFrame(index=[1]) & DataFrame(index=[1,2])
+        assert_frame_equal(result,DataFrame(index=[1,2]))
+
+        result = DataFrame(index=[1],columns=['A']) & DataFrame(index=[1],columns=['A'])
+        assert_frame_equal(result,DataFrame(index=[1],columns=['A']))
+
+        result = DataFrame(True,index=[1],columns=['A']) & DataFrame(True,index=[1],columns=['A'])
+        assert_frame_equal(result,DataFrame(True,index=[1],columns=['A']))
+
+        result = DataFrame(True,index=[1],columns=['A']) | DataFrame(True,index=[1],columns=['A'])
+        assert_frame_equal(result,DataFrame(True,index=[1],columns=['A']))
+
+        # boolean ops
+        result = DataFrame(1,index=[1],columns=['A']) | DataFrame(True,index=[1],columns=['A'])
+        assert_frame_equal(result,DataFrame(1,index=[1],columns=['A']))
+
+        def f():
+            DataFrame(1.0,index=[1],columns=['A']) | DataFrame(True,index=[1],columns=['A'])
+        self.assertRaises(TypeError, f)
+
+        def f():
+            DataFrame('foo',index=[1],columns=['A']) | DataFrame(True,index=[1],columns=['A'])
+        self.assertRaises(TypeError, f)
+
     def test_operators_none_as_na(self):
         df = DataFrame({"col1": [2, 5.0, 123, None],
                         "col2": [1, 2, 3, 4]}, dtype=object)