id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
2052694433,PR_kwDOAMm_X85ilhQm,8565,Faster encoding functions.,2448579,closed,0,,,1,2023-12-21T16:05:02Z,2024-01-04T14:25:45Z,2024-01-04T14:25:43Z,MEMBER,,0,pydata/xarray/pulls/8565,"Spotted when profiling some write workloads.
1. Speeds up the check for multi-index
2. Speeds up one string encoder by not re-creating variables when not necessary.

@benbovy is there a better way?","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/8565/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
2052952379,I_kwDOAMm_X856XZE7,8568,Raise when assigning attrs to virtual variables (default coordinate arrays),2448579,open,0,,,0,2023-12-21T19:24:11Z,2023-12-21T19:24:19Z,,MEMBER,,,,"### Discussed in https://github.com/pydata/xarray/discussions/8567

<div type='discussions-op-text'>

<sup>Originally posted by **matthew-brett** December 21, 2023</sup>
Sorry for the introductory question, but we (@ivanov and I) ran into this behavior while experimenting:

```python
import numpy as np
data = np.zeros((3, 4, 5))
ds = xr.DataArray(data, dims=('i', 'j', 'k'))
print(ds['k'].attrs)
```

This shows `{}` as we might reasonably expect.  But then:

```python
ds['k'].attrs['foo'] = 'bar'
print(ds['k'].attrs)
```

This also gives `{}`, which we found surprising.   We worked out why that was, after a little experimentation (the default coordinate arrays seems to get created on the fly and garbage collected immediately).  But it took us a little while.   Is that as intended?  Is there a way of making this less confusing?

Thanks for any help.   </div>","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/8568/reactions"", ""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
2052610515,PR_kwDOAMm_X85ilOq9,8564,Fix mypy type ignore,2448579,closed,0,,,1,2023-12-21T15:15:26Z,2023-12-21T15:41:13Z,2023-12-21T15:24:52Z,MEMBER,,0,pydata/xarray/pulls/8564,,"{""url"": ""https://api.github.com/repos/pydata/xarray/issues/8564/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull