Pull xarray's nbytes from nbytes attribute on arrays

doc/api.rst

@@ -282,7 +282,6 @@ ndarray attributes
    DataArray.shape
    DataArray.size
    DataArray.dtype
-   DataArray.nbytes
    DataArray.chunks
 
 

xarray/core/dataarray.py

@@ -646,6 +646,12 @@ def size(self) -> int:
 
     @property
     def nbytes(self) -> int:
+        """
+        Total bytes consumed by the elements of this DataArray's data.
+
+        If the backend data array does not include ``nbytes``, estimates
+        the bytes consumed based on the ``size`` and ``dtype``.
+        """
         return self.variable.nbytes
 
     @property

xarray/core/dataset.py

@@ -1378,6 +1378,12 @@ def __array__(self, dtype=None):
 
     @property
     def nbytes(self) -> int:
+        """
+        Total bytes consumed by the data arrays of all variables in this dataset.
+
+        If the backend array for any variable does not include ``nbytes``, estimates
+        the total bytes for that array based on the ``size`` and ``dtype``.
+        """
         return sum(v.nbytes for v in self.variables.values())
 
     @property

xarray/core/variable.py

@@ -335,7 +335,13 @@ def shape(self):
 
     @property
     def nbytes(self):
-        return self.size * self.dtype.itemsize
+        """
+        Total bytes consumed by the elements of the data array.
+        """
+        if hasattr(self.data, "nbytes"):
+            return self.data.nbytes
+        else:
+            return self.size * self.dtype.itemsize
 
     @property
     def _in_memory(self):

xarray/tests/test_array_api.py

@@ -43,6 +43,12 @@ def test_indexing(arrays) -> None:
     assert_equal(actual, expected)
 
 
+def test_properties(arrays) -> None:
+    np_arr, xp_arr = arrays
+    assert np_arr.nbytes == 48
+    assert xp_arr.nbytes == 48
+
+
 def test_reorganizing_operation(arrays) -> None:
     np_arr, xp_arr = arrays
     expected = np_arr.transpose()