I have similar problems with time coordinate. How did you solve your problem in the end?

I also list my problem here.

The following are my commands in a jupyter notebook

import xarray as xr import numpy as np import pandas as pd import sys

dset=xr.open_dataset("input/ts_Amon_CNRM-CM6-1_piControl_r1i1p1f2_gr_185001-234912.nc",decode_times=False) dset['time'] = pd.period_range(start='1850-01-15', end='2349-12-15', freq='M') varname="ts" anom = dset[varname].groupby('time.month')-dset[varname].groupby('time.month').mean('time', keep_attrs=True)

Then, I got the following error message.

---

KeyError Traceback (most recent call last) ~/miniconda3/envs/python_tutorial/lib/python3.9/site-packages/xarray/core/dataarray.py in _getitem_coord(self, key) 692 try: --> 693 var = self._coords[key] 694 except KeyError:

KeyError: 'time.month'

During handling of the above exception, another exception occurred:

AttributeError Traceback (most recent call last) <ipython-input-1-250a6867750b> in <module> 7 dset['time'] = pd.period_range(start='1850-01-15', end='2349-12-15', freq='M') 8 varname="ts" ----> 9 anom = dset[varname].groupby('time.month')-dset[varname].groupby('time.month').mean('time', keep_attrs=True)

~/miniconda3/envs/python_tutorial/lib/python3.9/site-packages/xarray/core/common.py in groupby(self, group, squeeze, restore_coord_dims) 703 ) 704 --> 705 return self._groupby_cls( 706 self, group, squeeze=squeeze, restore_coord_dims=restore_coord_dims 707 )

~/miniconda3/envs/python_tutorial/lib/python3.9/site-packages/xarray/core/groupby.py in init(self, obj, group, squeeze, grouper, bins, restore_coord_dims, cut_kwargs) 313 f"Received {group!r} instead." 314 ) --> 315 group = obj[group] 316 if len(group) == 0: 317 raise ValueError(f"{group.name} must not be empty")

~/miniconda3/envs/python_tutorial/lib/python3.9/site-packages/xarray/core/dataarray.py in getitem(self, key) 702 def getitem(self, key: Any) -> "DataArray": 703 if isinstance(key, str): --> 704 return self._getitem_coord(key) 705 else: 706 # xarray-style array indexing

~/miniconda3/envs/python_tutorial/lib/python3.9/site-packages/xarray/core/dataarray.py in getitem_coord(self, key) 694 except KeyError: 695 dim_sizes = dict(zip(self.dims, self.shape)) --> 696 , key, var = _get_virtual_variable( 697 self._coords, key, self._level_coords, dim_sizes 698 )

~/miniconda3/envs/python_tutorial/lib/python3.9/site-packages/xarray/core/dataset.py in _get_virtual_variable(variables, key, level_vars, dim_sizes) 179 data = getattr(ref_var.dt, var_name).data 180 else: --> 181 data = getattr(ref_var, var_name).data 182 virtual_var = Variable(ref_var.dims, data) 183

AttributeError: 'IndexVariable' object has no attribute 'month'