Add missing DataArray.dt.total_seconds() method (#8435)

Author: maresb

doc/api.rst

@@ -557,6 +557,7 @@ Datetimelike properties
    DataArray.dt.seconds
    DataArray.dt.microseconds
    DataArray.dt.nanoseconds
+   DataArray.dt.total_seconds
 
 **Timedelta methods**:
 

doc/whats-new.rst

@@ -24,6 +24,8 @@ New Features
 
 - Use `opt_einsum <https://optimized-einsum.readthedocs.io/en/stable/>`_ for :py:func:`xarray.dot` by default if installed.
   By `Deepak Cherian <https://github.com/dcherian>`_. (:issue:`7764`, :pull:`8373`).
+- Add ``DataArray.dt.total_seconds()`` method to match the Pandas API. (:pull:`8435`).
+  By `Ben Mares <https://github.com/maresb>`_.
 
 Breaking changes
 ~~~~~~~~~~~~~~~~

xarray/core/accessor_dt.py

@@ -74,6 +74,8 @@ def _access_through_series(values, name):
     if name == "season":
         months = values_as_series.dt.month.values
         field_values = _season_from_months(months)
+    elif name == "total_seconds":
+        field_values = values_as_series.dt.total_seconds().values
     elif name == "isocalendar":
         # special NaT-handling can be removed when
         # https://github.com/pandas-dev/pandas/issues/54657 is resolved
@@ -574,6 +576,13 @@ class TimedeltaAccessor(TimeAccessor[T_DataArray]):
            43200, 64800])
     Coordinates:
       * time     (time) timedelta64[ns] 1 days 00:00:00 ... 5 days 18:00:00
+    >>> ts.dt.total_seconds()
+    <xarray.DataArray 'total_seconds' (time: 20)>
+    array([ 86400., 108000., 129600., 151200., 172800., 194400., 216000.,
+           237600., 259200., 280800., 302400., 324000., 345600., 367200.,
+           388800., 410400., 432000., 453600., 475200., 496800.])
+    Coordinates:
+      * time     (time) timedelta64[ns] 1 days 00:00:00 ... 5 days 18:00:00
     """
 
     @property
@@ -596,6 +605,11 @@ def nanoseconds(self) -> T_DataArray:
         """Number of nanoseconds (>= 0 and less than 1 microsecond) for each element"""
         return self._date_field("nanoseconds", np.int64)
 
+    # Not defined as a property in order to match the Pandas API
+    def total_seconds(self) -> T_DataArray:
+        """Total duration of each element expressed in seconds."""
+        return self._date_field("total_seconds", np.float64)
+
 
 class CombinedDatetimelikeAccessor(
     DatetimeAccessor[T_DataArray], TimedeltaAccessor[T_DataArray]

xarray/tests/test_accessor_dt.py

@@ -6,6 +6,7 @@
 
 import xarray as xr
 from xarray.tests import (
+    assert_allclose,
     assert_array_equal,
     assert_chunks_equal,
     assert_equal,
@@ -100,6 +101,19 @@ def test_field_access(self, field) -> None:
         assert expected.dtype == actual.dtype
         assert_identical(expected, actual)
 
+    def test_total_seconds(self) -> None:
+        # Subtract a value in the middle of the range to ensure that some values
+        # are negative
+        delta = self.data.time - np.datetime64("2000-01-03")
+        actual = delta.dt.total_seconds()
+        expected = xr.DataArray(
+            np.arange(-48, 52, dtype=np.float64) * 3600,
+            name="total_seconds",
+            coords=[self.data.time],
+        )
+        # This works with assert_identical when pandas is >=1.5.0.
+        assert_allclose(expected, actual)
+
     @pytest.mark.parametrize(
         "field, pandas_field",
         [