id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
859933298,MDU6SXNzdWU4NTk5MzMyOTg=,5171,Dask now supports item assignment. Shouldn't xarray support it too?,9049976,closed,0,,,2,2021-04-16T15:38:40Z,2021-05-01T23:35:44Z,2021-05-01T23:35:44Z,CONTRIBUTOR,,,,"As of a few weeks ago, dask now supports [item assignment](https://github.com/dask/dask/commit/a199302b0c69df82a09c8ab166de882368e6e8c8). [Documentation here](https://docs.dask.org/en/latest/array-assignment.html).

At the moment, xarray prevents item assignment if a DataArray uses dask arrays.
```
>>> import xarray as xr
>>> foo = xr.DataArray([1,2,3,4,5,6], dims=('x'), coords={'x':[1,2,3,4,5,6]}).chunk(2)
>>> foo.loc[1] = 44
Traceback (most recent call last):
  File ""<stdin>"", line 1, in <module>
  File ""/home/tammas/miniconda3/envs/da/lib/python3.8/site-packages/xarray/core/dataarray.py"", line 213, in __setitem__
    self.data_array[pos_indexers] = value
  File ""/home/tammas/miniconda3/envs/da/lib/python3.8/site-packages/xarray/core/dataarray.py"", line 724, in __setitem__
    self.variable[key] = value
  File ""/home/tammas/miniconda3/envs/da/lib/python3.8/site-packages/xarray/core/variable.py"", line 889, in __setitem__
    indexable[index_tuple] = value
  File ""/home/tammas/miniconda3/envs/da/lib/python3.8/site-packages/xarray/core/indexing.py"", line 1379, in __setitem__
    raise TypeError(
TypeError: this variable's data is stored in a dask array, which does not support item assignment. To assign to this variable, you must first load it into memory explicitly using the .load() method or accessing its .values attribute.
```

Now that this is possible in dask, shouldn't xarray allow it too if the installed dask version supports it?

Kind regards,
Tam
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