issues: 1307501602

What happened?

When I generate a stacked multiindex coordinate dataset python ds = xr.Dataset( data_vars={"d": (["x", "y"], np.random.randn(2, 3))}, coords={"x": [3, 4], "y": [0.5, 1.2, 2.0]}, ) ds2 = ds.stack({"z": ["x", "y"]}) indexing the unstacked version of the data ds with both an integer as well as a float value python ds.sel(x=3) ds.sel(y=1.2) works without a problem. But if I try to index the stacked version ds2 python ds2.sel(x=3) ds2.sel(y=1.2) the integer indexing works, but the float indexing ds2.sel(y=1.2) fails with an InvalidIndexError.

The pandas version works without any problem: python df = ds2["d"].to_pandas() df[:, 1.2]

The problems seems to lie in xarray.core.utils.py in the maybe_cast_to_coords_dtype function python def maybe_cast_to_coords_dtype(label, coords_dtype): if coords_dtype.kind == "f" and not isinstance(label, slice): label = np.asarray(label, dtype=coords_dtype) return label that explicitly calls np.asarray on the coordinate label. This then later fails in pandas.core.indexes via the _check_indexing_error method, where it is checked that the label is a scalar, which it was before maybe_cast_to_coords_dtype converted it. Why does this conversion happen there at all?

What did you expect to happen?

Expecting ds2.sel(x=3) to return: python <xarray.Dataset> Dimensions: (x: 2) Coordinates: * x (x) int64 3 4 Data variables: d (x) int64 1 4

Minimal Complete Verifiable Example

Python import xarray as xr ds = xr.Dataset( data_vars={"d": (["x", "y"], [[0, 1, 2], [3, 4, 5]])}, coords={"x": [3, 4], "y": [0.5, 1.2, 2.0]}, ) ds2 = ds.stack({"z": ["x", "y"]}) ds2.sel(y=1.2)

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 Traceback (most recent call last):

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 3621, in get_loc return self._engine.get_loc(casted_key)

File "pandas/_libs/index.pyx", line 136, in pandas._libs.index.IndexEngine.get_loc

File "pandas/_libs/index.pyx", line 142, in pandas._libs.index.IndexEngine.get_loc

TypeError: '1.2' is an invalid key

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/spyder_kernels/py3compat.py", line 356, in compat_exec exec(code, globals, locals)

File "~/data_import.py", line 65, in <module> xr.Dataset(

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/xarray/core/dataset.py", line 2501, in sel pos_indexers, new_indexes = remap_label_indexers(

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/xarray/core/coordinates.py", line 421, in remap_label_indexers pos_indexers, new_indexes = indexing.remap_label_indexers(

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/xarray/core/indexing.py", line 121, in remap_label_indexers idxr, new_idx = index.query(labels, method=method, tolerance=tolerance)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/xarray/core/indexes.py", line 353, in query indexer, new_index = self.index.get_loc_level(

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/multi.py", line 2972, in get_loc_level loc, mi = self._get_loc_level(key, level=level)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/multi.py", line 3005, in _get_loc_level loc, new_index = self._get_loc_level(k, level=lev)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/multi.py", line 3113, in _get_loc_level indexer = self._get_level_indexer(key, level=level)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/multi.py", line 3222, in _get_level_indexer idx = self._get_loc_single_level_index(level_index, key)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/multi.py", line 2802, in _get_loc_single_level_index return level_index.get_loc(key)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 3628, in get_loc self._check_indexing_error(key)

File "~/.miniconda3/envs/artiq/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 5637, in _check_indexing_error raise InvalidIndexError(key)

InvalidIndexError: 1.2 ```

Anything else we need to know?

No response

Environment

INSTALLED VERSIONS ------------------ commit: None python: 3.8.13 | packaged by conda-forge | (default, Mar 25 2022, 06:04:10) [GCC 10.3.0] python-bits: 64 OS: Linux OS-release: 5.17.5-76051705-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: ('en_US', 'UTF-8') libhdf5: 1.12.1 libnetcdf: 4.8.1 xarray: 2022.3.0 pandas: 1.4.3 numpy: 1.23.1 scipy: 1.8.1 netCDF4: 1.6.0 pydap: None h5netcdf: 1.0.1 h5py: 3.7.0 Nio: None zarr: 2.12.0 cftime: 1.6.1 nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None dask: None distributed: None matplotlib: 3.5.2 cartopy: None seaborn: None numbagg: None fsspec: None cupy: None pint: None sparse: None setuptools: 63.2.0 pip: 22.1.2 conda: None pytest: None IPython: 7.33.0 sphinx: 5.0.2 /home/thorsten/.miniconda3/envs/artiq/lib/python3.8/site-packages/_distutils_hack/__init__.py:33: UserWarning: Setuptools is replacing distutils. warnings.warn("Setuptools is replacing distutils.")