BUG: DateOffset addition with non-nano (#55595)

jbrockmendel · mroeschke · web-flow · commit a5e55fb563b1 · 2023-10-19T15:54:24.000-07:00
* BUG: DateOffset addition with non-nano

* Update doc/source/whatsnew/v2.2.0.rst

Co-authored-by: Matthew Roeschke &lt;10647082+mroeschke@users.noreply.github.com&gt;

---------

Co-authored-by: Matthew Roeschke &lt;10647082+mroeschke@users.noreply.github.com&gt;
diff --git a/doc/source/whatsnew/v2.2.0.rst b/doc/source/whatsnew/v2.2.0.rst
@@ -303,6 +303,7 @@ Datetimelike
 - Bug in :meth:`DatetimeIndex.union` returning object dtype for tz-aware indexes with the same timezone but different units (:issue:`55238`)
 - Bug in :meth:`Tick.delta` with very large ticks raising ``OverflowError`` instead of ``OutOfBoundsTimedelta`` (:issue:`55503`)
 - Bug in adding or subtracting a :class:`Week` offset to a ``datetime64`` :class:`Series`, :class:`Index`, or :class:`DataFrame` column with non-nanosecond resolution returning incorrect results (:issue:`55583`)
+- Bug in addition or subtraction of :class:`DateOffset` objects with microsecond components to ``datetime64`` :class:`Index`, :class:`Series`, or :class:`DataFrame` columns with non-nanosecond resolution (:issue:`55595`)
 - Bug in addition or subtraction of very large :class:`Tick` objects with :class:`Timestamp` or :class:`Timedelta` objects raising ``OverflowError`` instead of ``OutOfBoundsTimedelta`` (:issue:`55503`)
 -
 
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
@@ -1368,10 +1368,10 @@ cdef class RelativeDeltaOffset(BaseOffset):
         else:
             return other + timedelta(self.n)
 
-    @apply_array_wraps
-    def _apply_array(self, dtarr):
-        reso = get_unit_from_dtype(dtarr.dtype)
-        dt64other = np.asarray(dtarr)
+    @cache_readonly
+    def _pd_timedelta(self) -> Timedelta:
+        # components of _offset that can be cast to pd.Timedelta
+
         kwds = self.kwds
         relativedelta_fast = {
             "years",
@@ -1385,28 +1385,26 @@ cdef class RelativeDeltaOffset(BaseOffset):
         }
         # relativedelta/_offset path only valid for base DateOffset
         if self._use_relativedelta and set(kwds).issubset(relativedelta_fast):
-
-            months = (kwds.get("years", 0) * 12 + kwds.get("months", 0)) * self.n
-            if months:
-                shifted = shift_months(dt64other.view("i8"), months, reso=reso)
-                dt64other = shifted.view(dtarr.dtype)
-
-            weeks = kwds.get("weeks", 0) * self.n
-            if weeks:
-                delta = Timedelta(days=7 * weeks)
-                td = (<_Timedelta>delta)._as_creso(reso)
-                dt64other = dt64other + td
-
-            timedelta_kwds = {
-                k: v
-                for k, v in kwds.items()
-                if k in ["days", "hours", "minutes", "seconds", "microseconds"]
+            td_kwds = {
+                key: val
+                for key, val in kwds.items()
+                if key in ["days", "hours", "minutes", "seconds", "microseconds"]
             }
-            if timedelta_kwds:
-                delta = Timedelta(**timedelta_kwds)
-                td = (<_Timedelta>delta)._as_creso(reso)
-                dt64other = dt64other + (self.n * td)
-            return dt64other
+            if "weeks" in kwds:
+                days = td_kwds.get("days", 0)
+                td_kwds["days"] = days + 7 * kwds["weeks"]
+
+            if td_kwds:
+                delta = Timedelta(**td_kwds)
+                if "microseconds" in kwds:
+                    delta = delta.as_unit("us")
+                else:
+                    delta = delta.as_unit("s")
+            else:
+                delta = Timedelta(0).as_unit("s")
+
+            return delta * self.n
+
         elif not self._use_relativedelta and hasattr(self, "_offset"):
             # timedelta
             num_nano = getattr(self, "nanoseconds", 0)
@@ -1415,8 +1413,12 @@ cdef class RelativeDeltaOffset(BaseOffset):
                 delta = Timedelta((self._offset + rem_nano) * self.n)
             else:
                 delta = Timedelta(self._offset * self.n)
-            td = (<_Timedelta>delta)._as_creso(reso)
-            return dt64other + td
+                if "microseconds" in kwds:
+                    delta = delta.as_unit("us")
+                else:
+                    delta = delta.as_unit("s")
+            return delta
+
         else:
             # relativedelta with other keywords
             kwd = set(kwds) - relativedelta_fast
@@ -1426,6 +1428,20 @@ cdef class RelativeDeltaOffset(BaseOffset):
                 "applied vectorized"
             )
 
+    @apply_array_wraps
+    def _apply_array(self, dtarr):
+        reso = get_unit_from_dtype(dtarr.dtype)
+        dt64other = np.asarray(dtarr)
+
+        delta = self._pd_timedelta  # may raise NotImplementedError
+
+        kwds = self.kwds
+        months = (kwds.get("years", 0) * 12 + kwds.get("months", 0)) * self.n
+        if months:
+            shifted = shift_months(dt64other.view("i8"), months, reso=reso)
+            dt64other = shifted.view(dtarr.dtype)
+        return dt64other + delta
+
     def is_on_offset(self, dt: datetime) -> bool:
         if self.normalize and not _is_normalized(dt):
             return False
diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
@@ -799,14 +799,17 @@ def _add_offset(self, offset) -> Self:
             values = self
 
         try:
-            result = offset._apply_array(values).view(values.dtype)
+            result = offset._apply_array(values)
+            if result.dtype.kind == "i":
+                result = result.view(values.dtype)
         except NotImplementedError:
             warnings.warn(
                 "Non-vectorized DateOffset being applied to Series or DatetimeIndex.",
                 PerformanceWarning,
                 stacklevel=find_stack_level(),
             )
             result = self.astype("O") + offset
+            # TODO(GH#55564): as_unit will be unnecessary
             result = type(self)._from_sequence(result).as_unit(self.unit)
             if not len(self):
                 # GH#30336 _from_sequence won't be able to infer self.tz
diff --git a/pandas/tests/arithmetic/test_datetime64.py b/pandas/tests/arithmetic/test_datetime64.py
@@ -1223,13 +1223,16 @@ class TestDatetime64DateOffsetArithmetic:
     # Tick DateOffsets
 
     # TODO: parametrize over timezone?
-    def test_dt64arr_series_add_tick_DateOffset(self, box_with_array):
+    @pytest.mark.parametrize("unit", ["s", "ms", "us", "ns"])
+    def test_dt64arr_series_add_tick_DateOffset(self, box_with_array, unit):
         # GH#4532
         # operate with pd.offsets
-        ser = Series([Timestamp("20130101 9:01"), Timestamp("20130101 9:02")])
+        ser = Series(
+            [Timestamp("20130101 9:01"), Timestamp("20130101 9:02")]
+        ).dt.as_unit(unit)
         expected = Series(
             [Timestamp("20130101 9:01:05"), Timestamp("20130101 9:02:05")]
-        )
+        ).dt.as_unit(unit)
 
         ser = tm.box_expected(ser, box_with_array)
         expected = tm.box_expected(expected, box_with_array)
@@ -1310,7 +1313,8 @@ def test_dti_add_tick_tzaware(self, tz_aware_fixture, box_with_array):
     # -------------------------------------------------------------
     # RelativeDelta DateOffsets
 
-    def test_dt64arr_add_sub_relativedelta_offsets(self, box_with_array):
+    @pytest.mark.parametrize("unit", ["s", "ms", "us", "ns"])
+    def test_dt64arr_add_sub_relativedelta_offsets(self, box_with_array, unit):
         # GH#10699
         vec = DatetimeIndex(
             [
@@ -1323,7 +1327,7 @@ def test_dt64arr_add_sub_relativedelta_offsets(self, box_with_array):
                 Timestamp("2000-05-15"),
                 Timestamp("2001-06-15"),
             ]
-        )
+        ).as_unit(unit)
         vec = tm.box_expected(vec, box_with_array)
         vec_items = vec.iloc[0] if box_with_array is pd.DataFrame else vec
 
@@ -1337,24 +1341,29 @@ def test_dt64arr_add_sub_relativedelta_offsets(self, box_with_array):
             ("seconds", 2),
             ("microseconds", 5),
         ]
-        for i, (unit, value) in enumerate(relative_kwargs):
-            off = DateOffset(**{unit: value})
+        for i, (offset_unit, value) in enumerate(relative_kwargs):
+            off = DateOffset(**{offset_unit: value})
+
+            exp_unit = unit
+            if offset_unit == "microseconds" and unit != "ns":
+                exp_unit = "us"
 
-            expected = DatetimeIndex([x + off for x in vec_items])
+            # TODO(GH#55564): as_unit will be unnecessary
+            expected = DatetimeIndex([x + off for x in vec_items]).as_unit(exp_unit)
             expected = tm.box_expected(expected, box_with_array)
             tm.assert_equal(expected, vec + off)
 
-            expected = DatetimeIndex([x - off for x in vec_items])
+            expected = DatetimeIndex([x - off for x in vec_items]).as_unit(exp_unit)
             expected = tm.box_expected(expected, box_with_array)
             tm.assert_equal(expected, vec - off)
 
             off = DateOffset(**dict(relative_kwargs[: i + 1]))
 
-            expected = DatetimeIndex([x + off for x in vec_items])
+            expected = DatetimeIndex([x + off for x in vec_items]).as_unit(exp_unit)
             expected = tm.box_expected(expected, box_with_array)
             tm.assert_equal(expected, vec + off)
 
-            expected = DatetimeIndex([x - off for x in vec_items])
+            expected = DatetimeIndex([x - off for x in vec_items]).as_unit(exp_unit)
             expected = tm.box_expected(expected, box_with_array)
             tm.assert_equal(expected, vec - off)
             msg = "(bad|unsupported) operand type for unary"
diff --git a/pandas/tests/tseries/offsets/test_offsets.py b/pandas/tests/tseries/offsets/test_offsets.py
@@ -568,10 +568,8 @@ def test_add_dt64_ndarray_non_nano(self, offset_types, unit, request):
         # check that the result with non-nano matches nano
         off = _create_offset(offset_types)
 
-        dti = date_range("2016-01-01", periods=35, freq="D")
-
-        arr = dti._data._ndarray.astype(f"M8[{unit}]")
-        dta = type(dti._data)._simple_new(arr, dtype=arr.dtype)
+        dti = date_range("2016-01-01", periods=35, freq="D", unit=unit)
+        dta = dti._data
 
         expected = dti._data + off
         result = dta + off

Original file line number	Diff line number	Diff line change
`@@ -303,6 +303,7 @@ Datetimelike`
`303`	`303`	- Bug in :meth:`DatetimeIndex.union` returning object dtype for tz-aware indexes with the same timezone but different units (:issue:`55238`)
`304`	`304`	- Bug in :meth:`Tick.delta` with very large ticks raising ``OverflowError`` instead of ``OutOfBoundsTimedelta`` (:issue:`55503`)
`305`	`305`	- Bug in adding or subtracting a :class:`Week` offset to a ``datetime64`` :class:`Series`, :class:`Index`, or :class:`DataFrame` column with non-nanosecond resolution returning incorrect results (:issue:`55583`)
	`306`	+- Bug in addition or subtraction of :class:`DateOffset` objects with microsecond components to ``datetime64`` :class:`Index`, :class:`Series`, or :class:`DataFrame` columns with non-nanosecond resolution (:issue:`55595`)
`306`	`307`	- Bug in addition or subtraction of very large :class:`Tick` objects with :class:`Timestamp` or :class:`Timedelta` objects raising ``OverflowError`` instead of ``OutOfBoundsTimedelta`` (:issue:`55503`)
`307`	`308`	`-`
`308`	`309`