Coarsen keep attrs 3376 (#3801)

* Add test of DataWithCoords.coarsen() for #3376

* Add test of Variable.coarsen() for #3376

* Add keep_attrs kwarg to DataWithCoords.coarsen() for #3376

* Style and spelling fixes (#3376)

* Fix test_coarsen_keep_attrs by removing self from input

* Pass keep_attrs through to _coarsen_cls and _rolling_cls returns (#3376)

* Move keyword from coarsen to mean in test_coarsen_keep_attrs

* Start handling keep_attrs in rolling class constructors (#3376)

* Update Coarsen constructor and DatasetCoarsen class method (GH3376)

Assign keep_attrs keyword value to Coarsen objects in constructor
Add conditional inside _reduce_method.wrapped_func branching on self.keep_attrs and pass back to returned Dataset

* Incorporate code review from @max-sixty

* Fix Dataset.coarsen and Variable.coarsen for GH3376

Handle global keep_attrs setting inside Variable._coarsen_reshape

Pass attrs through consistently inside DatasetCoarsen._reduce_method

Don't pass Variable.coarsen a keyword argument it doesn't expect inside DataArrayCoarsen._reduce_method

* Update tests for GH3376

* Incorporate review changes to test_dataset for GH3376

Remove commented-out test from test_coarsen_keep_attrs

Add test_rolling_keep_attrs

* Change Rolling._dataset_implementation for GH3376

Return a Dataset object that results in test_rolling_keep_attrs Passing

* style fixes

* Remove duplicate variable assignment and document change (GH3776)

doc/whats-new.rst

@@ -61,6 +61,11 @@ Bug fixes
 - xarray now respects the over, under and bad colors if set on a provided colormap.
   (:issue:`3590`, :pull:`3601`)
   By `johnomotani <https://github.com/johnomotani>`_.
+- :py:func:`coarsen` now respects ``xr.set_options(keep_attrs=True)``
+  to preserve attributes. :py:meth:`Dataset.coarsen` accepts a keyword
+  argument ``keep_attrs`` to change this setting. (:issue:`3376`,
+  :pull:`3801`) By `Andrew Thomas <https://github.com/amcnicho>`_.
+
 - Fix :py:meth:`xarray.core.dataset.Dataset.to_zarr` when using `append_dim` and `group`
   simultaneously. (:issue:`3170`). By `Matthias Meyer <https://github.com/niowniow>`_.
 

xarray/core/common.py

@@ -753,6 +753,7 @@ def rolling(
         dim: Mapping[Hashable, int] = None,
         min_periods: int = None,
         center: bool = False,
+        keep_attrs: bool = None,
         **window_kwargs: int,
     ):
         """
@@ -769,6 +770,10 @@ def rolling(
             setting min_periods equal to the size of the window.
         center : boolean, default False
             Set the labels at the center of the window.
+        keep_attrs : bool, optional
+            If True, the object's attributes (`attrs`) will be copied from
+            the original object to the new one.  If False (default), the new
+            object will be returned without attributes.
         **window_kwargs : optional
             The keyword arguments form of ``dim``.
             One of dim or window_kwargs must be provided.
@@ -810,8 +815,13 @@ def rolling(
         core.rolling.DataArrayRolling
         core.rolling.DatasetRolling
         """
+        if keep_attrs is None:
+            keep_attrs = _get_keep_attrs(default=False)
+
         dim = either_dict_or_kwargs(dim, window_kwargs, "rolling")
-        return self._rolling_cls(self, dim, min_periods=min_periods, center=center)
+        return self._rolling_cls(
+            self, dim, min_periods=min_periods, center=center, keep_attrs=keep_attrs
+        )
 
     def rolling_exp(
         self,
@@ -859,6 +869,7 @@ def coarsen(
         boundary: str = "exact",
         side: Union[str, Mapping[Hashable, str]] = "left",
         coord_func: str = "mean",
+        keep_attrs: bool = None,
         **window_kwargs: int,
     ):
         """
@@ -879,8 +890,12 @@ def coarsen(
             multiple of the window size. If 'trim', the excess entries are
             dropped. If 'pad', NA will be padded.
         side : 'left' or 'right' or mapping from dimension to 'left' or 'right'
-        coord_func : function (name) that is applied to the coordintes,
+        coord_func : function (name) that is applied to the coordinates,
             or a mapping from coordinate name to function (name).
+        keep_attrs : bool, optional
+            If True, the object's attributes (`attrs`) will be copied from
+            the original object to the new one.  If False (default), the new
+            object will be returned without attributes.
 
         Returns
         -------
@@ -915,9 +930,17 @@ def coarsen(
         core.rolling.DataArrayCoarsen
         core.rolling.DatasetCoarsen
         """
+        if keep_attrs is None:
+            keep_attrs = _get_keep_attrs(default=False)
+
         dim = either_dict_or_kwargs(dim, window_kwargs, "coarsen")
         return self._coarsen_cls(
-            self, dim, boundary=boundary, side=side, coord_func=coord_func
+            self,
+            dim,
+            boundary=boundary,
+            side=side,
+            coord_func=coord_func,
+            keep_attrs=keep_attrs,
         )
 
     def resample(

xarray/core/rolling.py

@@ -7,6 +7,7 @@
 from . import dtypes, duck_array_ops, utils
 from .dask_array_ops import dask_rolling_wrapper
 from .ops import inject_reduce_methods
+from .options import _get_keep_attrs
 from .pycompat import dask_array_type
 
 try:
@@ -42,10 +43,10 @@ class Rolling:
     DataArray.rolling
     """
 
-    __slots__ = ("obj", "window", "min_periods", "center", "dim")
-    _attributes = ("window", "min_periods", "center", "dim")
+    __slots__ = ("obj", "window", "min_periods", "center", "dim", "keep_attrs")
+    _attributes = ("window", "min_periods", "center", "dim", "keep_attrs")
 
-    def __init__(self, obj, windows, min_periods=None, center=False):
+    def __init__(self, obj, windows, min_periods=None, center=False, keep_attrs=None):
         """
         Moving window object.
 
@@ -65,6 +66,10 @@ def __init__(self, obj, windows, min_periods=None, center=False):
             setting min_periods equal to the size of the window.
         center : boolean, default False
             Set the labels at the center of the window.
+        keep_attrs : bool, optional
+            If True, the object's attributes (`attrs`) will be copied from
+            the original object to the new one.  If False (default), the new
+            object will be returned without attributes.
 
         Returns
         -------
@@ -89,6 +94,10 @@ def __init__(self, obj, windows, min_periods=None, center=False):
         self.center = center
         self.dim = dim
 
+        if keep_attrs is None:
+            keep_attrs = _get_keep_attrs(default=False)
+        self.keep_attrs = keep_attrs
+
     @property
     def _min_periods(self):
         return self.min_periods if self.min_periods is not None else self.window
@@ -143,7 +152,7 @@ def count(self):
 class DataArrayRolling(Rolling):
     __slots__ = ("window_labels",)
 
-    def __init__(self, obj, windows, min_periods=None, center=False):
+    def __init__(self, obj, windows, min_periods=None, center=False, keep_attrs=None):
         """
         Moving window object for DataArray.
         You should use DataArray.rolling() method to construct this object
@@ -165,6 +174,10 @@ def __init__(self, obj, windows, min_periods=None, center=False):
             setting min_periods equal to the size of the window.
         center : boolean, default False
             Set the labels at the center of the window.
+        keep_attrs : bool, optional
+            If True, the object's attributes (`attrs`) will be copied from
+            the original object to the new one.  If False (default), the new
+            object will be returned without attributes.
 
         Returns
         -------
@@ -177,7 +190,11 @@ def __init__(self, obj, windows, min_periods=None, center=False):
         Dataset.rolling
         Dataset.groupby
         """
-        super().__init__(obj, windows, min_periods=min_periods, center=center)
+        if keep_attrs is None:
+            keep_attrs = _get_keep_attrs(default=False)
+        super().__init__(
+            obj, windows, min_periods=min_periods, center=center, keep_attrs=keep_attrs
+        )
 
         self.window_labels = self.obj[self.dim]
 
@@ -374,7 +391,7 @@ def _numpy_or_bottleneck_reduce(
 class DatasetRolling(Rolling):
     __slots__ = ("rollings",)
 
-    def __init__(self, obj, windows, min_periods=None, center=False):
+    def __init__(self, obj, windows, min_periods=None, center=False, keep_attrs=None):
         """
         Moving window object for Dataset.
         You should use Dataset.rolling() method to construct this object
@@ -396,6 +413,10 @@ def __init__(self, obj, windows, min_periods=None, center=False):
             setting min_periods equal to the size of the window.
         center : boolean, default False
             Set the labels at the center of the window.
+        keep_attrs : bool, optional
+            If True, the object's attributes (`attrs`) will be copied from
+            the original object to the new one.  If False (default), the new
+            object will be returned without attributes.
 
         Returns
         -------
@@ -408,15 +429,17 @@ def __init__(self, obj, windows, min_periods=None, center=False):
         Dataset.groupby
         DataArray.groupby
         """
-        super().__init__(obj, windows, min_periods, center)
+        super().__init__(obj, windows, min_periods, center, keep_attrs)
         if self.dim not in self.obj.dims:
             raise KeyError(self.dim)
         # Keep each Rolling object as a dictionary
         self.rollings = {}
         for key, da in self.obj.data_vars.items():
             # keeps rollings only for the dataset depending on slf.dim
             if self.dim in da.dims:
-                self.rollings[key] = DataArrayRolling(da, windows, min_periods, center)
+                self.rollings[key] = DataArrayRolling(
+                    da, windows, min_periods, center, keep_attrs
+                )
 
     def _dataset_implementation(self, func, **kwargs):
         from .dataset import Dataset
@@ -427,7 +450,8 @@ def _dataset_implementation(self, func, **kwargs):
                 reduced[key] = func(self.rollings[key], **kwargs)
             else:
                 reduced[key] = self.obj[key]
-        return Dataset(reduced, coords=self.obj.coords)
+        attrs = self.obj.attrs if self.keep_attrs else {}
+        return Dataset(reduced, coords=self.obj.coords, attrs=attrs)
 
     def reduce(self, func, **kwargs):
         """Reduce the items in this group by applying `func` along some
@@ -466,7 +490,7 @@ def _numpy_or_bottleneck_reduce(
             **kwargs,
         )
 
-    def construct(self, window_dim, stride=1, fill_value=dtypes.NA):
+    def construct(self, window_dim, stride=1, fill_value=dtypes.NA, keep_attrs=None):
         """
         Convert this rolling object to xr.Dataset,
         where the window dimension is stacked as a new dimension
@@ -487,6 +511,9 @@ def construct(self, window_dim, stride=1, fill_value=dtypes.NA):
 
         from .dataset import Dataset
 
+        if keep_attrs is None:
+            keep_attrs = _get_keep_attrs(default=True)
+
         dataset = {}
         for key, da in self.obj.data_vars.items():
             if self.dim in da.dims:
@@ -509,10 +536,18 @@ class Coarsen:
     DataArray.coarsen
     """
 
-    __slots__ = ("obj", "boundary", "coord_func", "windows", "side", "trim_excess")
+    __slots__ = (
+        "obj",
+        "boundary",
+        "coord_func",
+        "windows",
+        "side",
+        "trim_excess",
+        "keep_attrs",
+    )
     _attributes = ("windows", "side", "trim_excess")
 
-    def __init__(self, obj, windows, boundary, side, coord_func):
+    def __init__(self, obj, windows, boundary, side, coord_func, keep_attrs):
         """
         Moving window object.
 
@@ -541,6 +576,7 @@ def __init__(self, obj, windows, boundary, side, coord_func):
         self.windows = windows
         self.side = side
         self.boundary = boundary
+        self.keep_attrs = keep_attrs
 
         absent_dims = [dim for dim in windows.keys() if dim not in self.obj.dims]
         if absent_dims:
@@ -626,6 +662,11 @@ def _reduce_method(cls, func: Callable, include_skipna: bool, numeric_only: bool
         def wrapped_func(self, **kwargs):
             from .dataset import Dataset
 
+            if self.keep_attrs:
+                attrs = self.obj.attrs
+            else:
+                attrs = {}
+
             reduced = {}
             for key, da in self.obj.data_vars.items():
                 reduced[key] = da.variable.coarsen(
@@ -644,7 +685,7 @@ def wrapped_func(self, **kwargs):
                     )
                 else:
                     coords[c] = v.variable
-            return Dataset(reduced, coords=coords)
+            return Dataset(reduced, coords=coords, attrs=attrs)
 
         return wrapped_func
 

xarray/core/variable.py

@@ -1949,6 +1949,9 @@ def _coarsen_reshape(self, windows, boundary, side):
             else:
                 shape.append(variable.shape[i])
 
+        keep_attrs = _get_keep_attrs(default=False)
+        variable.attrs = variable._attrs if keep_attrs else {}
+
         return variable.data.reshape(shape), tuple(axes)
 
     @property

xarray/tests/test_dataset.py

@@ -5664,6 +5664,62 @@ def test_coarsen_coords_cftime():
     np.testing.assert_array_equal(actual.time, expected_times)
 
 
+def test_coarsen_keep_attrs():
+    _attrs = {"units": "test", "long_name": "testing"}
+
+    var1 = np.linspace(10, 15, 100)
+    var2 = np.linspace(5, 10, 100)
+    coords = np.linspace(1, 10, 100)
+
+    ds = Dataset(
+        data_vars={"var1": ("coord", var1), "var2": ("coord", var2)},
+        coords={"coord": coords},
+        attrs=_attrs,
+    )
+
+    # Test dropped attrs
+    dat = ds.coarsen(coord=5).mean()
+    assert dat.attrs == {}
+
+    # Test kept attrs using dataset keyword
+    dat = ds.coarsen(coord=5, keep_attrs=True).mean()
+    assert dat.attrs == _attrs
+
+    # Test kept attrs using global option
+    with set_options(keep_attrs=True):
+        dat = ds.coarsen(coord=5).mean()
+    assert dat.attrs == _attrs
+
+
+def test_rolling_keep_attrs():
+    _attrs = {"units": "test", "long_name": "testing"}
+
+    var1 = np.linspace(10, 15, 100)
+    var2 = np.linspace(5, 10, 100)
+    coords = np.linspace(1, 10, 100)
+
+    ds = Dataset(
+        data_vars={"var1": ("coord", var1), "var2": ("coord", var2)},
+        coords={"coord": coords},
+        attrs=_attrs,
+    )
+
+    # Test dropped attrs
+    dat = ds.rolling(dim={"coord": 5}, min_periods=None, center=False).mean()
+    assert dat.attrs == {}
+
+    # Test kept attrs using dataset keyword
+    dat = ds.rolling(
+        dim={"coord": 5}, min_periods=None, center=False, keep_attrs=True
+    ).mean()
+    assert dat.attrs == _attrs
+
+    # Test kept attrs using global option
+    with set_options(keep_attrs=True):
+        dat = ds.rolling(dim={"coord": 5}, min_periods=None, center=False).mean()
+    assert dat.attrs == _attrs
+
+
 def test_rolling_properties(ds):
     # catching invalid args
     with pytest.raises(ValueError, match="exactly one dim/window should"):

xarray/tests/test_variable.py

@@ -9,7 +9,7 @@
 import pytz
 
 from xarray import Coordinate, Dataset, IndexVariable, Variable, set_options
-from xarray.core import dtypes, indexing
+from xarray.core import dtypes, duck_array_ops, indexing
 from xarray.core.common import full_like, ones_like, zeros_like
 from xarray.core.indexing import (
     BasicIndexer,
@@ -1879,6 +1879,26 @@ def test_coarsen_2d(self):
         expected = self.cls(("x", "y"), [[10, 18], [42, 35]])
         assert_equal(actual, expected)
 
+    # perhaps @pytest.mark.parametrize("operation", [f for f in duck_array_ops])
+    def test_coarsen_keep_attrs(self, operation="mean"):
+        _attrs = {"units": "test", "long_name": "testing"}
+
+        test_func = getattr(duck_array_ops, operation, None)
+
+        # Test dropped attrs
+        with set_options(keep_attrs=False):
+            new = Variable(["coord"], np.linspace(1, 10, 100), attrs=_attrs).coarsen(
+                windows={"coord": 1}, func=test_func, boundary="exact", side="left"
+            )
+        assert new.attrs == {}
+
+        # Test kept attrs
+        with set_options(keep_attrs=True):
+            new = Variable(["coord"], np.linspace(1, 10, 100), attrs=_attrs).coarsen(
+                windows={"coord": 1}, func=test_func, boundary="exact", side="left"
+            )
+        assert new.attrs == _attrs
+
 
 @requires_dask
 class TestVariableWithDask(VariableSubclassobjects):