issues

• [x] Closes #8116, #3536
• [x] Tests added
• [ ] User visible changes (including notable bug fixes) are documented in whats-new.rst
• [ ] New functions/methods are listed in api.rst

Because the DataArray in a DataSet's data variable when saving to zarr, the incorrect metadata update behaviour applies to it. This is an attempt to fix the TODO left by PR5252. The tests are passing, but as I'm quite new to this repo, I'm not sure what cases should be tested as well. @shoyer could you share some insight please?

What happened?

When using the new functionality of calling to_zarr on DataArrays, I've noticed that the attributes are not updated and can only be set once, on initial archive creation. In our case, we are performing sequential writes to the Zarr regions and also want to update attributes. Regular Zarr API allows updating metadata and it also works with Datasets, so we suspect it's an issue with DataArrays. In fact, when calling to_zarr, the DataArray is converted to a Dataset, but when we check it, it does not have its attributes, as they live inside the nested array.

What did you expect to happen?

I would like to update attributes in the same manner as with plain Zarr or with Datasets. Currently, we have to resort to modifying the .zmetadata JSON and consider this dangerous and hacky.

Minimal Complete Verifiable Example

```Python import xarray as xr

ds_path = "ds" xr.Dataset().assign_attrs(a=1).to_zarr(ds_path, mode="w") xr.open_dataset(ds_path, engine="zarr").assign_attrs(b=2).to_zarr(ds_path, mode="a")

da_path = "da" xr.DataArray().assign_attrs(a=1).to_zarr(da_path, mode="w") xr.open_dataarray(da_path, engine="zarr").assign_attrs(b=2).to_zarr(da_path, mode="a")

print(xr.open_dataset(ds_path, engine="zarr").attrs == xr.open_dataarray(da_path, engine="zarr").attrs) ```

MVCE confirmation

• [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [X] Complete example — the example is self-contained, including all data and the text of any traceback.
• [X] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [X] New issue — a search of GitHub Issues suggests this is not a duplicate.

Relevant log output

No response

Anything else we need to know?

No response

Environment

• [x] Closes #7552
• [x] Tests added
• [x] User visible changes (including notable bug fixes) are documented in whats-new.rst

Implements @headtr1ck solution from the issue.

What happened?

Hi, I'm trying to create a DataArray with coordinates that are tuples and potentionally even more dimensional objects. The way I did it is to create an empty numpy array with dtype=object and then insert my tuples inside. This doesn't throw an error when creating a DataArray (as opposed to using a 2D ndarray or a list of lists). However, when trying to save it to zarr or netcdf. I get an error saying ValueError: setting an array element with a sequence

What did you expect to happen?

I want to be able to save and load such coordinates without errors. Maybe there is a cleaner way to do it than the object dtype ndarray?

Minimal Complete Verifiable Example

Python n = 5 x = np.empty(n, dtype=object) for i in range(n): x[i] = (i, i) xr.DataArray(np.arange(n), dims=("x"), coords={"x": x}).to_zarr("test")

MVCE confirmation

• [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [X] Complete example — the example is self-contained, including all data and the text of any traceback.
• [X] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [X] New issue — a search of GitHub Issues suggests this is not a duplicate.

Relevant log output

```Python File c:\Users\Wiktor\AppData\Local\pypoetry\Cache\virtualenvs\spin1-JGuolXDk-py3.11\Lib\site-packages\xarray\core\dataarray.py:4014, in DataArray.to_netcdf(self, path, mode, format, group, engine, encoding, unlimited_dims, compute, invalid_netcdf) 4010 else: 4011 # No problems with the name - so we're fine! 4012 dataset = self.to_dataset() -> 4014 return to_netcdf( # type: ignore # mypy cannot resolve the overloads:( 4015 dataset, 4016 path, 4017 mode=mode, 4018 format=format, 4019 group=group, 4020 engine=engine, 4021 encoding=encoding, 4022 unlimited_dims=unlimited_dims, ... 101 result = np.empty(data.shape, dtype) --> 102 result[...] = data 103 return result

ValueError: setting an array element with a sequence. ```

Anything else we need to know?

No response

Environment