Multidimensional Groupby --- ValueError: zip() argument 2 is longer than argument 1 #10739
Description
What is your issue?
I am trying to select a group from a multidimensional groupby.
import xarray as xr
from xarray.groupers import BinGrouper, UniqueGrouper
ds = xr.Dataset(
{"foo": (("x", "y"), np.random.rand(4, 3))},
coords={"x": [10, 20, 30, 40], "letters": ("x", list("abba"))},
)
groups = ds.groupby(x=BinGrouper(bins=[5, 15, 25]), letters=UniqueGrouper())If I try groups.groups, it returns:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Cell In[34], [line 1](vscode-notebook-cell:?execution_count=34&line=1)
----> [1](vscode-notebook-cell:?execution_count=34&line=1) groups.groups
File ~/projects/active/swot_longterm_finescale/.pixi/envs/default/lib/python3.13/site-packages/xarray/core/groupby.py:824, in GroupBy.groups(self)
822 # provided to mimic pandas.groupby
823 if self._groups is None:
--> [824](https://vscode-remote+ssh-002dremote-002bcoonamessett.vscode-resource.vscode-cdn.net/home/iury/projects/active/swot_longterm_finescale/swot_longterm_finescale/~/projects/active/swot_longterm_finescale/.pixi/envs/default/lib/python3.13/site-packages/xarray/core/groupby.py:824) self._groups = dict(
825 zip(
826 self.encoded.unique_coord.data,
827 self.encoded.group_indices,
828 strict=True,
829 )
830 )
831 return self._groups
ValueError: zip() argument 2 is longer than argument 1The code is the MWE, using the example from the documentation.
I am using xarray version 2025.9.0.