BUG: Fix boolean comparison with a DataFrame on the lhs, and a list/tuple on the rhs GH4576

doc/source/release.rst

@@ -283,6 +283,7 @@ See :ref:`Internal Refactoring<whatsnew_0130.refactoring>`
     in csv_import (:issue:`4322`)
   - Fix an issue with CacheableOffset not properly being used by many DateOffset; this prevented
     the DateOffset from being cached (:issue:`4609`)
+  - Fix boolean comparison with a DataFrame on the lhs, and a list/tuple on the rhs (:issue:`4576`)
 
 pandas 0.12
 ===========

pandas/core/internals.py

@@ -723,29 +723,65 @@ def eval(self, func, other, raise_on_error=True, try_cast=False):
         # make sure that we can broadcast
         is_transposed = False
         if hasattr(other, 'ndim') and hasattr(values, 'ndim'):
-            if values.ndim != other.ndim or values.shape == other.shape[::-1]:
-                values = values.T
-                is_transposed = True
+            if values.ndim != other.ndim:
+                    is_transposed = True
+            else:
+                if values.shape == other.shape[::-1]:
+                    is_transposed = True
+                elif values.shape[0] == other.shape[-1]:
+                    is_transposed = True
+                else:
+                    # this is a broadcast error heree
+                    raise ValueError("cannot broadcast shape [%s] with block values [%s]"
+                                     % (values.T.shape,other.shape))
+
+        transf = (lambda x: x.T) if is_transposed else (lambda x: x)
+
+        # coerce/transpose the args if needed
+        values, other = self._try_coerce_args(transf(values), other)
+
+        # get the result, may need to transpose the other
+        def get_result(other):
+            return self._try_coerce_result(func(values, other))
+
+        # error handler if we have an issue operating with the function
+        def handle_error():
 
-        values, other = self._try_coerce_args(values, other)
-        args = [values, other]
-        try:
-            result = self._try_coerce_result(func(*args))
-        except (Exception) as detail:
             if raise_on_error:
-                raise TypeError('Could not operate [%s] with block values [%s]'
+                raise TypeError('Could not operate %s with block values %s'
                                 % (repr(other), str(detail)))
             else:
                 # return the values
                 result = np.empty(values.shape, dtype='O')
                 result.fill(np.nan)
+                return result
+
+        # get the result
+        try:
+            result = get_result(other)
+
+        # if we have an invalid shape/broadcast error
+        # GH4576, so raise instead of allowing to pass thru
+        except (ValueError) as detail:
+            raise
+        except (Exception) as detail:
+            result = handle_error()
 
+        # technically a broadcast error in numpy can 'work' by returning a boolean False
         if not isinstance(result, np.ndarray):
-            raise TypeError('Could not compare [%s] with block values'
-                            % repr(other))
+            if not isinstance(result, np.ndarray):
+
+                # differentiate between an invalid ndarray-ndarray comparsion and
+                # an invalid type comparison
+                if isinstance(values, np.ndarray) and is_list_like(other):
+                    raise ValueError('Invalid broadcasting comparison [%s] with block values'
+                                     % repr(other))
+
+                raise TypeError('Could not compare [%s] with block values'
+                                % repr(other))
 
-        if is_transposed:
-            result = result.T
+        # transpose if needed
+        result = transf(result)
 
         # try to cast if requested
         if try_cast:

pandas/tests/test_frame.py

@@ -4709,6 +4709,75 @@ def test_float_none_comparison(self):
 
         self.assertRaises(TypeError, df.__eq__, None)
 
+    def test_boolean_comparison(self):
+
+        # GH 4576
+        # boolean comparisons with a tuple/list give unexpected results
+        df = DataFrame(np.arange(6).reshape((3,2)))
+        b = np.array([2, 2])
+        b_r = np.atleast_2d([2,2])
+        b_c = b_r.T
+        l = (2,2,2)
+        tup = tuple(l)
+
+        # gt
+        expected = DataFrame([[False,False],[False,True],[True,True]])
+        result = df>b
+        assert_frame_equal(result,expected)
+
+        result = df.values>b
+        assert_array_equal(result,expected.values)
+
+        result = df>l
+        assert_frame_equal(result,expected)
+
+        result = df>tup
+        assert_frame_equal(result,expected)
+
+        result = df>b_r
+        assert_frame_equal(result,expected)
+
+        result = df.values>b_r
+        assert_array_equal(result,expected.values)
+
+        self.assertRaises(ValueError, df.__gt__, b_c)
+        self.assertRaises(ValueError, df.values.__gt__, b_c)
+
+        # ==
+        expected = DataFrame([[False,False],[True,False],[False,False]])
+        result = df == b
+        assert_frame_equal(result,expected)
+
+        result = df==l
+        assert_frame_equal(result,expected)
+
+        result = df==tup
+        assert_frame_equal(result,expected)
+
+        result = df == b_r
+        assert_frame_equal(result,expected)
+
+        result = df.values == b_r
+        assert_array_equal(result,expected.values)
+
+        self.assertRaises(ValueError, lambda : df == b_c)
+        self.assert_((df.values == b_c) is False)
+
+        # with alignment
+        df = DataFrame(np.arange(6).reshape((3,2)),columns=list('AB'),index=list('abc'))
+        expected.index=df.index
+        expected.columns=df.columns
+
+        result = df==l
+        assert_frame_equal(result,expected)
+
+        result = df==tup
+        assert_frame_equal(result,expected)
+
+        # not shape compatible
+        self.assertRaises(ValueError, lambda : df == (2,2))
+        self.assertRaises(ValueError, lambda : df == [2,2])
+
     def test_to_csv_deprecated_options(self):
 
         pname = '__tmp_to_csv_deprecated_options__'