issues: 1466586967

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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
1466586967 I_kwDOAMm_X85XaldX 7328 Zarr store array dtype changes for empty object string 85085 closed 0     2 2022-11-28T15:05:14Z 2023-06-16T03:56:16Z 2023-06-16T03:56:16Z CONTRIBUTOR      

What happened?

Saving a dataset with an empty object (string) variable to zarr changes the dtype to float64.

What did you expect to happen?

The dtype should remain as O, just as it does for non-empty object variables.

Minimal Complete Verifiable Example

```Python import numpy as np import xarray as xr ds = xr.Dataset({"a": np.array([], dtype="O")}) ds["a"].dtype

prints: dtype('O')

ds.to_zarr("a.zarr") ds = xr.open_dataset("a.zarr") ds["a"].dtype

prints: dtype('float64')

```

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

INSTALLED VERSIONS ------------------ commit: None python: 3.8.13 (default, Mar 28 2022, 06:16:26) [Clang 12.0.0 ] python-bits: 64 OS: Darwin OS-release: 21.6.0 machine: x86_64 processor: i386 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: ('en_GB', 'UTF-8') libhdf5: None libnetcdf: None xarray: 2022.11.0 pandas: 1.5.0 numpy: 1.23.4 scipy: 1.9.2 netCDF4: None pydap: None h5netcdf: None h5py: None Nio: None zarr: 2.13.3 cftime: None nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None dask: 2022.10.0 distributed: 2022.10.0 matplotlib: 3.6.1 cartopy: None seaborn: 0.12.0 numbagg: None fsspec: 2022.8.2 cupy: None pint: None sparse: None flox: None numpy_groupies: None setuptools: 63.4.1 pip: 22.2.2 conda: None pytest: 7.1.3 IPython: 8.5.0 sphinx: 4.2.0 
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   completed 13221727 issue

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