Dispatch Series comparison ops to DatetimeIndex and TimedeltaIndex

Author: jbrockmendel

pandas/core/ops.py

@@ -741,6 +741,7 @@ def na_op(x, y):
         if is_categorical_dtype(x):
             return op(x, y)
         elif is_categorical_dtype(y) and not is_scalar(y):
+            # the `not is_scalar(y)` check avoids catching string "category"
             return op(y, x)
 
         elif is_object_dtype(x.dtype):
@@ -750,7 +751,6 @@ def na_op(x, y):
             raise TypeError("invalid type comparison")
 
         else:
-
             # we want to compare like types
             # we only want to convert to integer like if
             # we are not NotImplemented, otherwise
@@ -759,23 +759,18 @@ def na_op(x, y):
 
             # we have a datetime/timedelta and may need to convert
             mask = None
-            if (needs_i8_conversion(x) or
-                    (not is_scalar(y) and needs_i8_conversion(y))):
-
-                if is_scalar(y):
-                    mask = isna(x)
-                    y = libindex.convert_scalar(x, com._values_from_object(y))
-                else:
-                    mask = isna(x) | isna(y)
-                    y = y.view('i8')
+            if not is_scalar(y) and needs_i8_conversion(y):
+                mask = isna(x) | isna(y)
+                y = y.view('i8')
                 x = x.view('i8')
 
-            try:
+            method = getattr(x, name, None)
+            if method is not None:
                 with np.errstate(all='ignore'):
                     result = getattr(x, name)(y)
                 if result is NotImplemented:
                     raise TypeError("invalid type comparison")
-            except AttributeError:
+            else:
                 result = op(x, y)
 
             if mask is not None and mask.any():
@@ -788,17 +783,36 @@ def wrapper(self, other, axis=None):
         if axis is not None:
             self._get_axis_number(axis)
 
+        res_name = _get_series_op_result_name(self, other)
+
         if isinstance(other, ABCDataFrame):  # pragma: no cover
             # Defer to DataFrame implementation; fail early
             return NotImplemented
 
+        elif isinstance(other, ABCSeries) and not self._indexed_same(other):
+            raise ValueError('Can only compare identically-labeled Series '
+                             'objects')
+
+        elif is_datetime64_dtype(self) or is_datetime64tz_dtype(self):
+            res_values = dispatch_to_index_op(op, self, other,
+                                              pd.DatetimeIndex)
+            return _construct_result(self, res_values,
+                                     index=self.index, name=res_name,
+                                     dtype=res_values.dtype)
+
+        elif is_timedelta64_dtype(self):
+            res_values = dispatch_to_index_op(op, self, other,
+                                              pd.TimedeltaIndex)
+            return _construct_result(self, res_values,
+                                     index=self.index, name=res_name,
+                                     dtype=res_values.dtype)
+
         elif isinstance(other, ABCSeries):
+            # By this point we know that self._indexed_same(other)
             name = com._maybe_match_name(self, other)
-            if not self._indexed_same(other):
-                msg = 'Can only compare identically-labeled Series objects'
-                raise ValueError(msg)
             res_values = na_op(self.values, other.values)
-            return self._constructor(res_values, index=self.index, name=name)
+            return self._constructor(res_values, index=self.index,
+                                     name=res_name)
 
         elif isinstance(other, (np.ndarray, pd.Index)):
             # do not check length of zerodim array
@@ -836,7 +850,7 @@ def wrapper(self, other, axis=None):
                 res = op(self.values, other)
         else:
             values = self.get_values()
-            if isinstance(other, (list, np.ndarray)):
+            if isinstance(other, list):
                 other = np.asarray(other)
 
             with np.errstate(all='ignore'):

pandas/tests/indexes/datetimes/test_partial_slicing.py

@@ -349,7 +349,7 @@ def test_loc_datetime_length_one(self):
 
     @pytest.mark.parametrize('datetimelike', [
         Timestamp('20130101'), datetime(2013, 1, 1),
-        date(2013, 1, 1), np.datetime64('2013-01-01T00:00', 'ns')])
+        np.datetime64('2013-01-01T00:00', 'ns')])
     @pytest.mark.parametrize('op,expected', [
         (op.lt, [True, False, False, False]),
         (op.le, [True, True, False, False]),

pandas/tests/series/test_arithmetic.py

@@ -43,6 +43,34 @@ def test_ser_flex_cmp_return_dtypes_empty(self, opname):
         result = getattr(empty, opname)(const).get_dtype_counts()
         tm.assert_series_equal(result, Series([1], ['bool']))
 
+    @pytest.mark.parametrize('op', [operator.eq, operator.ne,
+                                    operator.le, operator.lt,
+                                    operator.ge, operator.gt])
+    @pytest.mark.parametrize('names', [(None, None, None),
+                                       ('foo', 'bar', None),
+                                       ('baz', 'baz', 'baz')])
+    def test_ser_cmp_result_names(self, names, op):
+        # so far only for timedelta, and datetime dtypes
+
+        # datetime64 dtype
+        dti = pd.date_range('1949-06-07 03:00:00',
+                            freq='H', periods=5, name=names[0])
+        ser = Series(dti).rename(names[1])
+        result = op(ser, dti)
+        assert result.name == names[2]
+
+        # datetime64tz dtype
+        dti = dti.tz_localize('US/Central')
+        ser = Series(dti).rename(names[1])
+        result = op(ser, dti)
+        assert result.name == names[2]
+
+        # timedelta64 dtype
+        tdi = dti - dti.shift(1)
+        ser = Series(tdi).rename(names[1])
+        result = op(ser, tdi)
+        assert result.name == names[2]
+
 
 class TestTimestampSeriesComparison(object):
     def test_dt64ser_cmp_period_scalar(self):

pandas/tests/test_base.py

@@ -10,7 +10,7 @@
 import pandas as pd
 import pandas.compat as compat
 from pandas.core.dtypes.common import (
-    is_object_dtype, is_datetimetz,
+    is_object_dtype, is_datetimetz, is_datetime64_dtype,
     needs_i8_conversion)
 import pandas.util.testing as tm
 from pandas import (Series, Index, DatetimeIndex, TimedeltaIndex,
@@ -297,13 +297,21 @@ def test_none_comparison(self):
                 # assert result.iat[0]
                 # assert result.iat[1]
 
-                result = None > o
-                assert not result.iat[0]
-                assert not result.iat[1]
+                if is_datetime64_dtype(o) or is_datetimetz(o):
+                    # datetime dtypes follow conventions set by
+                    # Timestamp (via DatetimeIndex)
+                    with pytest.raises(TypeError):
+                        None > o
+                    with pytest.raises(TypeError):
+                        o > None
+                else:
+                    result = None > o
+                    assert not result.iat[0]
+                    assert not result.iat[1]
 
-                result = o < None
-                assert not result.iat[0]
-                assert not result.iat[1]
+                    result = o < None
+                    assert not result.iat[0]
+                    assert not result.iat[1]
 
     def test_ndarray_compat_properties(self):