Combining attrs of member DataArrays of Datasets #4017
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Need to pass combine_attrs="drop", to allow attrs_file to set the attrs.
johnomotani
commented
May 8, 2020
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| def test_open_mfdataset_dataarray_attr_by_coords(self): | ||
| """ | ||
| Case when an attribute of a member DataArray differs across the multiple files | ||
| """ | ||
| with self.setup_files_and_datasets() as (files, [ds1, ds2]): | ||
| # Give the files an inconsistent attribute | ||
| for i, f in enumerate(files): | ||
| ds = open_dataset(f).load() | ||
| ds["v1"].attrs["test_dataarray_attr"] = i | ||
| ds.close() | ||
| ds.to_netcdf(f) | ||
|
|
||
| with xr.open_mfdataset(files, combine="by_coords", concat_dim="t") as ds: | ||
| assert ds["v1"].test_dataarray_attr == 0 |
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@TomNicholas do you think we should make this test pass (i.e. support combining attrs on DataArrays contained in the Dataset being loaded)?
Proposal for a fix:
- Support
open_mfdataset-style attribute combining by upgrading thecombine_attrsargument tocombine_nested/combine_by_coords(and probably the other functions that have acombine_attrsargument) so it can be passed one of theDatasets orDataArrays being combined/merged, and will then take theattrsfrom that. - In
open_mfdatasetuse theattrs_fileargument to get theDatasetto take theattrsfrom, and pass that to thecombine_attrsargument ofcombine_nested/combine_by_coords.
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While looking at #4009, I noticed that the
combine_attrskwarg toconcatormergeonly affects the global attrs of theDataset, not the attrs ofDataArrayorVariablemembers of theDatasets being combined. I think this is a bug.So far this PR adds tests that reproduce the issue in #4009, and the issue described above. Fixing should be fairly simple: for #4009 pass
combine_attrs="drop"tocombine_by_coordsandcombine_nestedinopen_mfdataset; for this issue insert thecombine_attrshandling in an appropriate place - possibly inmerge.unique_variable. I'll update with fixes when I get a chance.isort -rc . && black . && mypy . && flake8whats-new.rstfor all changes andapi.rstfor new API