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  • tomwhite · 4 ✖

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  • CF encoding should preserve vlen dtype for empty arrays · 4 ✖

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id html_url issue_url node_id user created_at updated_at ▲ author_association body reactions performed_via_github_app issue
1573764660 https://github.com/pydata/xarray/pull/7862#issuecomment-1573764660 https://api.github.com/repos/pydata/xarray/issues/7862 IC_kwDOAMm_X85dzb40 tomwhite 85085 2023-06-02T13:44:43Z 2023-06-02T13:44:43Z CONTRIBUTOR

@kmuehlbauer thanks for adding tests! I'm not sure what the mypy error is either, I'm afraid...

 
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   CF encoding should preserve vlen dtype for empty arrays 1720045908
1561308333 https://github.com/pydata/xarray/pull/7862#issuecomment-1561308333 https://api.github.com/repos/pydata/xarray/issues/7862 IC_kwDOAMm_X85dD6yt tomwhite 85085 2023-05-24T14:51:23Z 2023-05-24T14:51:23Z CONTRIBUTOR

So it looks like the changes here with the fix in my branch will get your issue resolved @tomwhite, right?

Yes - thanks!

I'm a bit worried, that this might break other users workflows, if they depend on the current conversion to floating point for some reason.

The floating point default is preserved if you do e.g. xr.Dataset({"a": np.array([], dtype=object)}). The change here will only convert to string if there is extra metadata present that says it is a string.

 
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   CF encoding should preserve vlen dtype for empty arrays 1720045908
1561240314 https://github.com/pydata/xarray/pull/7862#issuecomment-1561240314 https://api.github.com/repos/pydata/xarray/issues/7862 IC_kwDOAMm_X85dDqL6 tomwhite 85085 2023-05-24T14:12:49Z 2023-05-24T14:12:49Z CONTRIBUTOR

Could you verify the above example, please?

The code looks fine, and I get the same result when I run it with this PR.

Your fix in https://github.com/kmuehlbauer/xarray/tree/preserve-vlen-string-dtype changes the metadata so it is correctly preserved as metadata: {'element_type': <class 'str'>}.

I feel less qualified to evaluate the impact of the netcdf4 fix.

 
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   CF encoding should preserve vlen dtype for empty arrays 1720045908
1561143111 https://github.com/pydata/xarray/pull/7862#issuecomment-1561143111 https://api.github.com/repos/pydata/xarray/issues/7862 IC_kwDOAMm_X85dDSdH tomwhite 85085 2023-05-24T13:23:18Z 2023-05-24T13:23:18Z CONTRIBUTOR

Thanks for taking a look @kmuehlbauer and for the useful example code. I hadn't considered the netcdf cases, so thanks for pointing those out.

Engine netcdf4 does not roundtrip here, losing the dtype metadata information. There is special casing for h5netcdf backend, though.

Could netcdf4 do the same special-casing as h5netcdf?

 
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   CF encoding should preserve vlen dtype for empty arrays 1720045908

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