issue_comments

Awesome, thanks @antarcticrainforest -- yes, it will always have an object dtype.

Are we expecting the CFTimeIndex object to always have "O" as dtype? If so the solution would be straight forward. Which means I can create a PR.

Thanks @antarcticrainforest -- I think that's exactly what @mathause is getting at. It seems fairly safe to add a new keyword argument to CFTimeIndex.__new__, and the example @mathause uses would make a nice test. Would either of you be up to make a PR?

I just ran into the very same issue. Are you sure that this is a problem with pandas? I've had a look into the pandas changes between 1.3.X and 1.4.X. Apparently the _new_Index method, which gets involved when serialising the index object, has been changed:

elif "dtype" not in d and "data" in d: # Prevent Index.__new__ from conducting inference; # "data" key not in RangeIndex d["dtype"] = d["data"].dtype return cls.__new__(cls, **d)

the problem is, that __new__ doesn't except a dtype argument. I've tried adding a dtype argument and it works. So I guess since this class inherits from pd.Index it needs to be updated?

Smaller repro

python import xarray as xr import pickle t = xr.cftime_range("20010101", "20010520") pickle.loads(pickle.dumps(t)) Looks like pandas now passes dtype on to __new__ which CFTimeIndex.__new__ does not accept:

https://github.com/pydata/xarray/blob/fe491b14b113c185b5b9a18e4f643e5a73208629/xarray/coding/cftimeindex.py#L313

Might be pandas-dev/pandas#43188. So CFTimeIndex.__new__ might need to accept dtype? @spencerkclark

Update: It is pandas that is the critical package. Pinning distributed<2022.01.0, xarray<0.21.0 and cftime<1.5.2 didn't fix it, but adding pandas<1.4.0 makes the above test pass. Will now try unpinning other packages and confirm it is pandas that is the issue.

Edit: Confirmed it is pandas==1.4.0 that causes this issue. Following version combination does not produce this error: ``` INSTALLED VERSIONS

commit: None python: 3.9.10 | packaged by conda-forge | (main, Jan 30 2022, 18:04:04) [GCC 9.4.0] python-bits: 64 OS: Linux OS-release: 4.18.0-348.2.1.el8.nci.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: en_AU.utf8 LANG: en_AU.ISO8859-1 LOCALE: ('en_US', 'UTF-8') libhdf5: 1.10.6 libnetcdf: 4.7.4

xarray: 0.21.0 pandas: 1.3.5 numpy: 1.22.1 scipy: 1.7.3 netCDF4: 1.5.6 pydap: installed h5netcdf: 0.13.1 h5py: 3.6.0 Nio: None zarr: 2.10.3 cftime: 1.5.2 nc_time_axis: 1.4.0 PseudoNetCDF: None rasterio: 1.2.6 cfgrib: 0.9.10.0 iris: 3.1.0 bottleneck: 1.3.2 dask: 2022.01.1 distributed: 2022.01.1 matplotlib: 3.5.1 cartopy: 0.19.0.post1 seaborn: 0.11.2 numbagg: None fsspec: 2022.01.0 cupy: 10.1.0 pint: 0.18 sparse: 0.13.0 setuptools: 59.8.0 pip: 21.3.1 conda: 4.11.0 pytest: 6.2.5 IPython: 8.0.1 sphinx: 4.4.0 ```