drop_sel returns KeyError for abbreviated dates

[scottyhq]

What happened?

for a dataframe with a detailed timestamp coordinate (2022-03-11T13:50:50.551314000)

da.sel(time="2022-03-11") works but da.drop_sel(time="2022-03-11") results in a KeyError

What did you expect to happen?

i expect drop_sel() to work with the same inputs as sel()

Minimal Complete Verifiable Example

import numpy as np
import xarray as xr
times = np.array(['2022-03-03T13:50:49.548072000', '2022-03-11T13:50:50.551314000',
                  '2022-03-12T13:44:35.547024000', '2022-03-13T12:18:48.015182000'],
                  dtype='datetime64[ns]')

da = xr.DataArray(np.arange(4), dims="time", coords={"time": times})
da.drop_sel(time='2022-03-11')

A workaround is to use the exact datestring:

da.drop_sel(time='2022-03-11T13:50:50.551314000')

MVCE confirmation

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

Relevant log output

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
Cell In[4], line 1
----> 1 da.drop_sel(time='2022-03-11')

File ~/.local/envs/xvec/lib/python3.11/site-packages/xarray/core/dataarray.py:3105, in DataArray.drop_sel(self, labels, errors, **labels_kwargs)
   3102 if labels_kwargs or isinstance(labels, dict):
   3103     labels = either_dict_or_kwargs(labels, labels_kwargs, "drop")
-> 3105 ds = self._to_temp_dataset().drop_sel(labels, errors=errors)
   3106 return self._from_temp_dataset(ds)

File ~/.local/envs/xvec/lib/python3.11/site-packages/xarray/core/dataset.py:5292, in Dataset.drop_sel(self, labels, errors, **labels_kwargs)
   5290     except KeyError:
   5291         raise ValueError(f"dimension {dim!r} does not have coordinate labels")
-> 5292     new_index = index.drop(labels_for_dim, errors=errors)
   5293     ds = ds.loc[{dim: new_index}]
   5294 return ds

File ~/.local/envs/xvec/lib/python3.11/site-packages/pandas/core/indexes/base.py:6934, in Index.drop(self, labels, errors)
   6932 if mask.any():
   6933     if errors != "ignore":
-> 6934         raise KeyError(f"{list(labels[mask])} not found in axis")
   6935     indexer = indexer[~mask]
   6936 return self.delete(indexer)

KeyError: "['2022-03-11'] not found in axis"

Anything else we need to know?

related to #6605 (comment)

Environment

(xarray: 2023.3.0)

INSTALLED VERSIONS

commit: None
python: 3.11.0 | packaged by conda-forge | (main, Jan 14 2023, 12:27:40) [GCC 11.3.0]
python-bits: 64
OS: Linux
OS-release: 5.4.231-137.341.amzn2.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: en_US.UTF-8
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.12.2
libnetcdf: 4.9.1

xarray: 2023.3.0
pandas: 1.5.3
numpy: 1.24.2
scipy: 1.10.1
netCDF4: 1.6.3
pydap: None
h5netcdf: 1.1.0
h5py: 3.8.0
Nio: None
zarr: None
cftime: 1.6.2
nc_time_axis: None
PseudoNetCDF: None
rasterio: 1.3.6
cfgrib: None
iris: None
bottleneck: None
dask: None
distributed: None
matplotlib: 3.7.1
cartopy: None
seaborn: None
numbagg: None
fsspec: None
cupy: None
pint: None
sparse: None
flox: None
numpy_groupies: None
setuptools: 67.6.0
pip: 23.0.1
conda: None
pytest: None
mypy: None
IPython: 8.11.0
sphinx: None

[dcherian]

Thanks we definitely want everything that works for sel to work for drop_sel.

xarray/xarray/core/dataset.py

Line 5292 in 4448828

new_index = index.drop(labels_for_dim, errors=errors)

index.get_indexer(labels_for_dim) will get you the correct indices to drop. Though probably there's another method that could work.

cc @benbovy