BUG: Series contains NaT with object dtype comparison incorrect (pandas-dev#13592)

closes pandas-dev#9005

Author: sinhrks

doc/source/whatsnew/v0.19.0.txt

@@ -527,6 +527,8 @@ Bug Fixes
 - Bug in extension dtype creation where the created types were not is/identical (:issue:`13285`)
 
 - Bug in ``NaT`` - ``Period`` raises ``AttributeError`` (:issue:`13071`)
+- Bug in ``Series`` comparison may output incorrect result if rhs contains ``NaT`` (:issue:`9005`)
+- Bug in ``Series`` and ``Index`` comparison may output incorrect result if it contains ``NaT`` with ``object`` dtype (:issue:`13592`)
 - Bug in ``Period`` addition raises ``TypeError`` if ``Period`` is on right hand side (:issue:`13069`)
 - Bug in ``Peirod`` and ``Series`` or ``Index`` comparison raises ``TypeError`` (:issue:`13200`)
 - Bug in ``pd.set_eng_float_format()`` that would prevent NaN's from formatting (:issue:`11981`)

pandas/core/ops.py

@@ -27,7 +27,8 @@
                                 is_integer_dtype, is_categorical_dtype,
                                 is_object_dtype, is_timedelta64_dtype,
                                 is_datetime64_dtype, is_datetime64tz_dtype,
-                                is_bool_dtype, PerformanceWarning, ABCSeries)
+                                is_bool_dtype, PerformanceWarning,
+                                ABCSeries, ABCIndex)
 
 # -----------------------------------------------------------------------------
 # Functions that add arithmetic methods to objects, given arithmetic factory
@@ -664,6 +665,22 @@ def wrapper(left, right, name=name, na_op=na_op):
     return wrapper
 
 
+def _comp_method_OBJECT_ARRAY(op, x, y):
+    if isinstance(y, list):
+        y = lib.list_to_object_array(y)
+    if isinstance(y, (np.ndarray, ABCSeries, ABCIndex)):
+        if not is_object_dtype(y.dtype):
+            y = y.astype(np.object_)
+
+        if isinstance(y, (ABCSeries, ABCIndex)):
+            y = y.values
+
+        result = lib.vec_compare(x, y, op)
+    else:
+        result = lib.scalar_compare(x, y, op)
+    return result
+
+
 def _comp_method_SERIES(op, name, str_rep, masker=False):
     """
     Wrapper function for Series arithmetic operations, to avoid
@@ -680,16 +697,7 @@ def na_op(x, y):
             return op(y, x)
 
         if is_object_dtype(x.dtype):
-            if isinstance(y, list):
-                y = lib.list_to_object_array(y)
-
-            if isinstance(y, (np.ndarray, ABCSeries)):
-                if not is_object_dtype(y.dtype):
-                    result = lib.vec_compare(x, y.astype(np.object_), op)
-                else:
-                    result = lib.vec_compare(x, y, op)
-            else:
-                result = lib.scalar_compare(x, y, op)
+            result = _comp_method_OBJECT_ARRAY(op, x, y)
         else:
 
             # we want to compare like types
@@ -713,12 +721,11 @@ def na_op(x, y):
                     (not isscalar(y) and needs_i8_conversion(y))):
 
                 if isscalar(y):
+                    mask = isnull(x)
                     y = _index.convert_scalar(x, _values_from_object(y))
                 else:
+                    mask = isnull(x) | isnull(y)
                     y = y.view('i8')
-
-                mask = isnull(x)
-
                 x = x.view('i8')
 
             try:

pandas/indexes/base.py

@@ -31,6 +31,7 @@
                                 is_list_like, is_bool_dtype,
                                 is_integer_dtype, is_float_dtype,
                                 needs_i8_conversion)
+from pandas.core.ops import _comp_method_OBJECT_ARRAY
 from pandas.core.strings import StringAccessorMixin
 
 from pandas.core.config import get_option
@@ -3182,8 +3183,11 @@ def _evaluate_compare(self, other):
                 if needs_i8_conversion(self) and needs_i8_conversion(other):
                     return self._evaluate_compare(other, op)
 
-                func = getattr(self.values, op)
-                result = func(np.asarray(other))
+                if is_object_dtype(self) and self.nlevels == 1:
+                    # don't pass MultiIndex
+                    result = _comp_method_OBJECT_ARRAY(op, self.values, other)
+                else:
+                    result = op(self.values, np.asarray(other))
 
                 # technically we could support bool dtyped Index
                 # for now just return the indexing array directly
@@ -3196,12 +3200,12 @@ def _evaluate_compare(self, other):
 
             return _evaluate_compare
 
-        cls.__eq__ = _make_compare('__eq__')
-        cls.__ne__ = _make_compare('__ne__')
-        cls.__lt__ = _make_compare('__lt__')
-        cls.__gt__ = _make_compare('__gt__')
-        cls.__le__ = _make_compare('__le__')
-        cls.__ge__ = _make_compare('__ge__')
+        cls.__eq__ = _make_compare(operator.eq)
+        cls.__ne__ = _make_compare(operator.ne)
+        cls.__lt__ = _make_compare(operator.lt)
+        cls.__gt__ = _make_compare(operator.gt)
+        cls.__le__ = _make_compare(operator.le)
+        cls.__ge__ = _make_compare(operator.ge)
 
     @classmethod
     def _add_numericlike_set_methods_disabled(cls):

pandas/lib.pyx

@@ -768,12 +768,12 @@ def scalar_compare(ndarray[object] values, object val, object op):
         raise ValueError('Unrecognized operator')
 
     result = np.empty(n, dtype=bool).view(np.uint8)
-    isnull_val = _checknull(val)
+    isnull_val = checknull(val)
 
     if flag == cpython.Py_NE:
         for i in range(n):
             x = values[i]
-            if _checknull(x):
+            if checknull(x):
                 result[i] = True
             elif isnull_val:
                 result[i] = True
@@ -785,7 +785,7 @@ def scalar_compare(ndarray[object] values, object val, object op):
     elif flag == cpython.Py_EQ:
         for i in range(n):
             x = values[i]
-            if _checknull(x):
+            if checknull(x):
                 result[i] = False
             elif isnull_val:
                 result[i] = False
@@ -798,7 +798,7 @@ def scalar_compare(ndarray[object] values, object val, object op):
     else:
         for i in range(n):
             x = values[i]
-            if _checknull(x):
+            if checknull(x):
                 result[i] = False
             elif isnull_val:
                 result[i] = False
@@ -864,7 +864,7 @@ def vec_compare(ndarray[object] left, ndarray[object] right, object op):
             x = left[i]
             y = right[i]
 
-            if _checknull(x) or _checknull(y):
+            if checknull(x) or checknull(y):
                 result[i] = True
             else:
                 result[i] = cpython.PyObject_RichCompareBool(x, y, flag)
@@ -873,7 +873,7 @@ def vec_compare(ndarray[object] left, ndarray[object] right, object op):
             x = left[i]
             y = right[i]
 
-            if _checknull(x) or _checknull(y):
+            if checknull(x) or checknull(y):
                 result[i] = False
             else:
                 result[i] = cpython.PyObject_RichCompareBool(x, y, flag)

pandas/tests/series/test_operators.py

@@ -980,24 +980,97 @@ def test_comparison_invalid(self):
             self.assertRaises(TypeError, lambda: x <= y)
 
     def test_more_na_comparisons(self):
-        left = Series(['a', np.nan, 'c'])
-        right = Series(['a', np.nan, 'd'])
+        for dtype in [None, object]:
+            left = Series(['a', np.nan, 'c'], dtype=dtype)
+            right = Series(['a', np.nan, 'd'], dtype=dtype)
 
-        result = left == right
-        expected = Series([True, False, False])
-        assert_series_equal(result, expected)
+            result = left == right
+            expected = Series([True, False, False])
+            assert_series_equal(result, expected)
 
-        result = left != right
-        expected = Series([False, True, True])
-        assert_series_equal(result, expected)
+            result = left != right
+            expected = Series([False, True, True])
+            assert_series_equal(result, expected)
 
-        result = left == np.nan
-        expected = Series([False, False, False])
-        assert_series_equal(result, expected)
+            result = left == np.nan
+            expected = Series([False, False, False])
+            assert_series_equal(result, expected)
 
-        result = left != np.nan
-        expected = Series([True, True, True])
-        assert_series_equal(result, expected)
+            result = left != np.nan
+            expected = Series([True, True, True])
+            assert_series_equal(result, expected)
+
+    def test_nat_comparisons(self):
+        data = [([pd.Timestamp('2011-01-01'), pd.NaT,
+                  pd.Timestamp('2011-01-03')],
+                 [pd.NaT, pd.NaT, pd.Timestamp('2011-01-03')]),
+
+                ([pd.Timedelta('1 days'), pd.NaT,
+                  pd.Timedelta('3 days')],
+                 [pd.NaT, pd.NaT, pd.Timedelta('3 days')]),
+
+                ([pd.Period('2011-01', freq='M'), pd.NaT,
+                  pd.Period('2011-03', freq='M')],
+                 [pd.NaT, pd.NaT, pd.Period('2011-03', freq='M')])]
+
+        # add lhs / rhs switched data
+        data = data + [(r, l) for l, r in data]
+
+        for l, r in data:
+            for dtype in [None, object]:
+                left = Series(l, dtype=dtype)
+
+                # Series, Index
+                for right in [Series(r, dtype=dtype), Index(r, dtype=dtype)]:
+                    expected = Series([False, False, True])
+                    assert_series_equal(left == right, expected)
+
+                    expected = Series([True, True, False])
+                    assert_series_equal(left != right, expected)
+
+                    expected = Series([False, False, False])
+                    assert_series_equal(left < right, expected)
+
+                    expected = Series([False, False, False])
+                    assert_series_equal(left > right, expected)
+
+                    expected = Series([False, False, True])
+                    assert_series_equal(left >= right, expected)
+
+                    expected = Series([False, False, True])
+                    assert_series_equal(left <= right, expected)
+
+    def test_nat_comparisons_scalar(self):
+        data = [[pd.Timestamp('2011-01-01'), pd.NaT,
+                 pd.Timestamp('2011-01-03')],
+
+                [pd.Timedelta('1 days'), pd.NaT, pd.Timedelta('3 days')],
+
+                [pd.Period('2011-01', freq='M'), pd.NaT,
+                 pd.Period('2011-03', freq='M')]]
+
+        for l in data:
+            for dtype in [None, object]:
+                left = Series(l, dtype=dtype)
+
+                expected = Series([False, False, False])
+                assert_series_equal(left == pd.NaT, expected)
+                assert_series_equal(pd.NaT == left, expected)
+
+                expected = Series([True, True, True])
+                assert_series_equal(left != pd.NaT, expected)
+                assert_series_equal(pd.NaT != left, expected)
+
+                expected = Series([False, False, False])
+                assert_series_equal(left < pd.NaT, expected)
+                assert_series_equal(pd.NaT > left, expected)
+                assert_series_equal(left <= pd.NaT, expected)
+                assert_series_equal(pd.NaT >= left, expected)
+
+                assert_series_equal(left > pd.NaT, expected)
+                assert_series_equal(pd.NaT < left, expected)
+                assert_series_equal(left >= pd.NaT, expected)
+                assert_series_equal(pd.NaT <= left, expected)
 
     def test_comparison_different_length(self):
         a = Series(['a', 'b', 'c'])

pandas/tseries/base.py

@@ -142,7 +142,7 @@ def _evaluate_compare(self, other, op):
             other = type(self)(other)
 
         # compare
-        result = getattr(self.asi8, op)(other.asi8)
+        result = op(self.asi8, other.asi8)
 
         # technically we could support bool dtyped Index
         # for now just return the indexing array directly

pandas/tseries/tdi.py

@@ -36,7 +36,7 @@ def _td_index_cmp(opname, nat_result=False):
 
     def wrapper(self, other):
         func = getattr(super(TimedeltaIndex, self), opname)
-        if _is_convertible_to_td(other):
+        if _is_convertible_to_td(other) or other is tslib.NaT:
             other = _to_m8(other)
             result = func(other)
             if com.isnull(other):

pandas/tseries/tests/test_base.py

@@ -458,6 +458,32 @@ def test_sub_period(self):
             with tm.assertRaises(TypeError):
                 p - idx
 
+    def test_comp_nat(self):
+        left = pd.DatetimeIndex([pd.Timestamp('2011-01-01'), pd.NaT,
+                                 pd.Timestamp('2011-01-03')])
+        right = pd.DatetimeIndex([pd.NaT, pd.NaT, pd.Timestamp('2011-01-03')])
+
+        for l, r in [(left, right), (left.asobject, right.asobject)]:
+            result = l == r
+            expected = np.array([False, False, True])
+            tm.assert_numpy_array_equal(result, expected)
+
+            result = l != r
+            expected = np.array([True, True, False])
+            tm.assert_numpy_array_equal(result, expected)
+
+            expected = np.array([False, False, False])
+            tm.assert_numpy_array_equal(l == pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT == r, expected)
+
+            expected = np.array([True, True, True])
+            tm.assert_numpy_array_equal(l != pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT != l, expected)
+
+            expected = np.array([False, False, False])
+            tm.assert_numpy_array_equal(l < pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT > l, expected)
+
     def test_value_counts_unique(self):
         # GH 7735
         for tz in [None, 'UTC', 'Asia/Tokyo', 'US/Eastern']:
@@ -1238,6 +1264,32 @@ def test_addition_ops(self):
         expected = Timestamp('20130102')
         self.assertEqual(result, expected)
 
+    def test_comp_nat(self):
+        left = pd.TimedeltaIndex([pd.Timedelta('1 days'), pd.NaT,
+                                 pd.Timedelta('3 days')])
+        right = pd.TimedeltaIndex([pd.NaT, pd.NaT, pd.Timedelta('3 days')])
+
+        for l, r in [(left, right), (left.asobject, right.asobject)]:
+            result = l == r
+            expected = np.array([False, False, True])
+            tm.assert_numpy_array_equal(result, expected)
+
+            result = l != r
+            expected = np.array([True, True, False])
+            tm.assert_numpy_array_equal(result, expected)
+
+            expected = np.array([False, False, False])
+            tm.assert_numpy_array_equal(l == pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT == r, expected)
+
+            expected = np.array([True, True, True])
+            tm.assert_numpy_array_equal(l != pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT != l, expected)
+
+            expected = np.array([False, False, False])
+            tm.assert_numpy_array_equal(l < pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT > l, expected)
+
     def test_value_counts_unique(self):
         # GH 7735
 
@@ -2039,6 +2091,32 @@ def test_sub_isub(self):
         rng -= 1
         tm.assert_index_equal(rng, expected)
 
+    def test_comp_nat(self):
+        left = pd.PeriodIndex([pd.Period('2011-01-01'), pd.NaT,
+                               pd.Period('2011-01-03')])
+        right = pd.PeriodIndex([pd.NaT, pd.NaT, pd.Period('2011-01-03')])
+
+        for l, r in [(left, right), (left.asobject, right.asobject)]:
+            result = l == r
+            expected = np.array([False, False, True])
+            tm.assert_numpy_array_equal(result, expected)
+
+            result = l != r
+            expected = np.array([True, True, False])
+            tm.assert_numpy_array_equal(result, expected)
+
+            expected = np.array([False, False, False])
+            tm.assert_numpy_array_equal(l == pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT == r, expected)
+
+            expected = np.array([True, True, True])
+            tm.assert_numpy_array_equal(l != pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT != l, expected)
+
+            expected = np.array([False, False, False])
+            tm.assert_numpy_array_equal(l < pd.NaT, expected)
+            tm.assert_numpy_array_equal(pd.NaT > l, expected)
+
     def test_value_counts_unique(self):
         # GH 7735
         idx = pd.period_range('2011-01-01 09:00', freq='H', periods=10)