MCVE Code Sample

Create two conda environments: - conda create --name xr140 python xarray==0.14.0 ipython -y - conda create --name xr141 python xarray==0.14.1 ipython -y

The following works if you run all of it within the same environment. However, if you store it with xarray=0.14.0, and load it with xarray=0.14.1, then it fails.

```python import shelve import xarray as xr import numpy as np

data = xr.DataArray(data=np.arange(10), dims=["test"])

Store data

with shelve.open('test') as db: db['data'] = data

Load data

with shelve.open('test') as db: newdata = db['data']

np.allclose(data, newdata) ```

Expected Output

One should be able to load the pickle no matter what the version of xarray is.

Problem Description

Storing with xarray=0.14.0 and trying to load with xarray=0.14.1 results in the following output: ```

KeyError Traceback (most recent call last) ~/anaconda3/envs/xarray141/lib/python3.8/shelve.py in getitem(self, key) 110 try: --> 111 value = self.cache[key] 112 except KeyError:

KeyError: 'data'

During handling of the above exception, another exception occurred:

AttributeError Traceback (most recent call last) ~/anaconda3/envs/xarray141/lib/python3.8/site-packages/xarray/core/common.py in setattr(self, name, value) 261 try: --> 262 object.setattr(self, name, value) 263 except AttributeError as e:

AttributeError: 'DataArray' object has no attribute '_accessors'

The above exception was the direct cause of the following exception:

AttributeError Traceback (most recent call last) <ipython-input-1-f8dc3ae27b24> in <module> 5 # Load data 6 with shelve.open('test') as db: ----> 7 newdata = db['data'] 8

~/anaconda3/envs/xarray141/lib/python3.8/shelve.py in getitem(self, key) 112 except KeyError: 113 f = BytesIO(self.dict[key.encode(self.keyencoding)]) --> 114 value = Unpickler(f).load() 115 if self.writeback: 116 self.cache[key] = value

~/anaconda3/envs/xarray141/lib/python3.8/site-packages/xarray/core/common.py in setattr(self, name, value) 268 ): 269 raise --> 270 raise AttributeError( 271 "cannot set attribute %r on a %r object. Use setitem style" 272 "assignment (e.g., ds['name'] = ...) instead of assigning variables."

AttributeError: cannot set attribute '_accessors' on a 'DataArray' object. Use setitem styleassignment (e.g., ds['name'] = ...) instead of assigning variables. ```

Output of xr.show_versions()

The xr.show_versions() for the two environments are identical, except for the xarray versions.