issues: 1319724885

What happened?

python da = xr.DataArray(np.random.rand(4), {'x': np.arange(4)}) da = da.assign_coords(y=('x', np.linspace(0, 1, 4))) da = da.assign_coords(z=('x', np.arange(4) + 4)) da.set_index(x=["y", "z"]).sel(y=slice(None, 0.5)) fails with TypeError: float() argument must be a string or a real number, not 'slice'

What did you expect to happen?

In v2022.3, this yields the correct sliced selection. Also, in v2022.6 this works for Multiindices without float-Values python da = xr.DataArray(np.random.rand(4), {'x': np.arange(4)}) da = da.assign_coords(y=('x', np.arange(4))) da = da.assign_coords(z=('x', np.arange(4) + 4)) da.set_index(x=["y", "z"]).sel(y=slice(None, 2), z=slice(5, None)) (only that the resulting coordinates look a bit weird, containing slices). Also, the sliced selection for a regular float-based index works in v2202.6 python da = xr.DataArray(np.random.rand(4), {'x': np.linspace(0, 1, 4)}) da.sel(x=slice(None, 0.5))

Minimal Complete Verifiable Example

```Python import numpy as np import xarray as xr

da = xr.DataArray(np.random.rand(4), {'x': np.arange(4)}) da = da.assign_coords(y=('x', np.linspace(0, 1, 4))) da = da.assign_coords(z=('x', np.arange(4) + 4)) da.set_index(x=["y", "z"]).sel(y=slice(None, 0.5)) ```

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 File c:\mambaforge\envs\dev\lib\site-packages\xarray\core\dataarray.py:1420, in DataArray.sel(self, indexers, method, tolerance, drop, indexers_kwargs) 1310 def sel( 1311 self: T_DataArray, 1312 indexers: Mapping[Any, Any] = None, (...) 1316 indexers_kwargs: Any, 1317 ) -> T_DataArray: 1318 """Return a new DataArray whose data is given by selecting index 1319 labels along the specified dimension(s). 1320 (...) 1418 Dimensions without coordinates: points 1419 """ -> 1420 ds = self._to_temp_dataset().sel( 1421 indexers=indexers, 1422 drop=drop, 1423 method=method, 1424 tolerance=tolerance, ... 197 # see https://github.com/pydata/xarray/issues/5727 --> 198 value = np.asarray(value, dtype=dtype) 199 return value

TypeError: float() argument must be a string or a real number, not 'slice' ```

Anything else we need to know?

Maybe related to #6836

Environment

INSTALLED VERSIONS ------------------ commit: None python: 3.10.5 | packaged by conda-forge | (main, Jun 14 2022, 06:57:19) [MSC v.1929 64 bit (AMD64)] python-bits: 64 OS: Windows OS-release: 10 machine: AMD64 processor: Intel64 Family 6 Model 142 Stepping 12, GenuineIntel byteorder: little LC_ALL: None LANG: de_DE.UTF-8 LOCALE: ('de_DE', 'cp1252') libhdf5: None libnetcdf: None xarray: 2022.6.0 pandas: 1.4.3 numpy: 1.23.1 scipy: 1.8.1 netCDF4: None pydap: None h5netcdf: None h5py: None Nio: None zarr: None cftime: None 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: 0.11.2 numbagg: None fsspec: None cupy: None pint: 0.19.2 sparse: None flox: None numpy_groupies: None setuptools: 63.2.0 pip: 22.2 conda: None pytest: 7.1.2 IPython: 8.4.0 sphinx: 4.5.0