html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/1215#issuecomment-334259359,https://api.github.com/repos/pydata/xarray/issues/1215,334259359,MDEyOklzc3VlQ29tbWVudDMzNDI1OTM1OQ==,10050469,2017-10-04T19:09:55Z,2017-10-04T19:09:55Z,MEMBER,"@jhamman no I haven't looked into this any further (and I also forgot what my workaround at that time actually was).

I also think your example should work, and that we should never check for values on disk: if the dims and coordinates names match, write the variable and assume the coordinates are ok.

If the variable already exists on file, match the behavior of netCDF4 (I actually don't know what netCDF4 does in that case)","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,201428093
https://github.com/pydata/xarray/issues/1215#issuecomment-274319422,https://api.github.com/repos/pydata/xarray/issues/1215,274319422,MDEyOklzc3VlQ29tbWVudDI3NDMxOTQyMg==,10050469,2017-01-22T09:22:52Z,2017-01-22T12:50:58Z,MEMBER,"I see.

>  but perhaps we don't need to fix this for v0.9.

Agreed, but it would be good to get this working some day. For now I can see an easy workaround for my purposes.

 Another possibility would be to give the user control on whether existing variables should be ignored, overwritten or raise an error when appending to a file.    


 ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,201428093
https://github.com/pydata/xarray/issues/1215#issuecomment-273731575,https://api.github.com/repos/pydata/xarray/issues/1215,273731575,MDEyOklzc3VlQ29tbWVudDI3MzczMTU3NQ==,10050469,2017-01-19T10:05:59Z,2017-01-19T10:05:59Z,MEMBER,"I did a few tests: the regression happened in https://github.com/pydata/xarray/pull/1017

Something in the way coordinates variables have changes implies that the writing is happening differently now. The question is whether this should now be handled downstream (in the netcdf backend) or upstream (at the dataset level)?  ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,201428093
https://github.com/pydata/xarray/issues/1215#issuecomment-273441335,https://api.github.com/repos/pydata/xarray/issues/1215,273441335,MDEyOklzc3VlQ29tbWVudDI3MzQ0MTMzNQ==,10050469,2017-01-18T10:36:41Z,2017-01-18T10:36:41Z,MEMBER,"Note that the problems occurs because the backend wants to write the ``'dim'`` coordinate each time. At the second call, the coordinate variable already exists and this raises the error.




","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,201428093
https://github.com/pydata/xarray/issues/1215#issuecomment-273333969,https://api.github.com/repos/pydata/xarray/issues/1215,273333969,MDEyOklzc3VlQ29tbWVudDI3MzMzMzk2OQ==,10050469,2017-01-17T23:25:30Z,2017-01-17T23:25:30Z,MEMBER,"An even simpler example:

```python
import os
import xarray as xr

path = 'test.nc'
if os.path.exists(path):
    os.remove(path)
    
ds = xr.Dataset()
ds['dim'] = ('dim', [0, 1, 2])
ds['var1'] = ('dim', [10, 11, 12])
ds['var2'] = ('dim', [13, 14, 15])

ds[['var1']].to_netcdf(path)
ds[['var2']].to_netcdf(path, 'a')
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,201428093