pydata / pydata/xarray

Feature request: raise more informative error message for `xr.open_dataset(list_of_paths)`

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enhancement topic-backends topic-error reporting
Dominant language
Python
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Description

Is your feature request related to a problem?

I sometimes use xr.open_dataset instead of xr.open_mfdataset on multiple paths. I propose to raise a more informative error message than ValueError: did not find a match in any of xarray's currently installed IO backends ['netcdf4', 'h5netcdf', 'scipy', 'cfgrib']. Consider explicitly selecting one of the installed engines via the ``engine`` parameter, or installing additional IO dependencies, see: https://docs.xarray.dev/en/stable/getting-started-guide/installing.html https://docs.xarray.dev/en/stable/user-guide/io.html.

import xarray as xr

xr.__version__ # '2022.3.0'

ds = xr.tutorial.load_dataset("air_temperature")

ds.isel(time=slice(None,1500)).to_netcdf("file1.nc")
ds.isel(time=slice(1500,None)).to_netcdf("file2.nc")

xr.open_mfdataset(["file1.nc","file2.nc"]) # works
xr.open_mfdataset("file?.nc") # works

# I understand what I need to do here
xr.open_dataset("file?.nc") # fails FileNotFoundError: No such file or directory: b'/dir/file?.nc'

# I dont here; I also first try to check whether one of these files is corrupt
xr.open_dataset(["file1.nc","file2.nc"]) # fails ValueError: did not find a match in any of xarray's currently installed IO backends ['netcdf4', 'h5netcdf', 'scipy', 'cfgrib']. Consider explicitly selecting one of the installed engines via the ``engine`` parameter, or installing additional IO dependencies, see: links
Describe the solution you'd like

directing the user towards the solution, i.e. "found path as list, please use open_mfdataset"

Describe alternatives you've considered

No response

Additional context

No response

Contributor guide

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by tracing the open_dataset and open_mfdataset entry points using the reproducer in the issue. Check how a list of paths is handled and how the current backend error is raised. Done means a list passed to open_dataset produces a clear message directing the user to open_mfdataset, with tests covering the behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
backend-api-design
Issue type
Feature
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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