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/4471#issuecomment-703058067,https://api.github.com/repos/pydata/xarray/issues/4471,703058067,MDEyOklzc3VlQ29tbWVudDcwMzA1ODA2Nw==,500246,2020-10-03T06:59:07Z,2020-10-03T06:59:07Z,CONTRIBUTOR,"I can try to fix this in a PR, I just need to be sure what the fix should look like - to change the dimensionality of attributes (has the potential to break backward compatibility) or to adapt other components to handle either scalars or length 1 arrays (safer alternative, but may occur in more locations both inside and outside xarray, so in this case perhaps a note in the documentation could be in order as well).  I don't know if xarray thrives for consistency between what the different engines expose on opening the same file.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-702708138,https://api.github.com/repos/pydata/xarray/issues/4471,702708138,MDEyOklzc3VlQ29tbWVudDcwMjcwODEzOA==,500246,2020-10-02T12:32:40Z,2020-10-02T12:32:40Z,CONTRIBUTOR,"According to [The NetCDF User's Guide](https://www.unidata.ucar.edu/software/netcdf/docs/netcdf_data_set_components.html#Attributes), attributes are supposed to be vectors:

> The current version treats all attributes as vectors; scalar values are treated as single-element vectors.

That suggests that, strictly speaking, the h5netcdf engine is right and the netcdf4 engine is wrong, and that other components (such as where the scale factor and add_offset are applied) need to be adapted to handle arrays of length 1 for those values.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-702671253,https://api.github.com/repos/pydata/xarray/issues/4471,702671253,MDEyOklzc3VlQ29tbWVudDcwMjY3MTI1Mw==,500246,2020-10-02T11:07:33Z,2020-10-02T11:07:33Z,CONTRIBUTOR,"The `ds.load()` prevents the traceback because it means the entire n-d data variable is multiplied with the 1-d scale factor.  Similarly, requesting a slice (`ds[""Rad""][400:402, 300:302]`) also prevents a traceback.  The traceback occurs if a single value is requested, because then Python will complain about multiplying a scalar with a 1-d array.  I'm not entirely sure why, but would be a numpy issue:

```
In [7]: a = np.array(0)

In [8]: b = np.array([0])

In [9]: a * b
Out[9]: array([0])

In [10]: a *= b
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-10-0d04f348f081> in <module>
----> 1 a *= b

ValueError: non-broadcastable output operand with shape () doesn't match the broadcast shape (1,)
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-702645270,https://api.github.com/repos/pydata/xarray/issues/4471,702645270,MDEyOklzc3VlQ29tbWVudDcwMjY0NTI3MA==,500246,2020-10-02T10:10:45Z,2020-10-02T10:10:45Z,CONTRIBUTOR,"Interestingly, the problem is prevented if one adds

`ds.load()`

before the print statement.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-702643539,https://api.github.com/repos/pydata/xarray/issues/4471,702643539,MDEyOklzc3VlQ29tbWVudDcwMjY0MzUzOQ==,500246,2020-10-02T10:07:17Z,2020-10-02T10:07:34Z,CONTRIBUTOR,"My last comment was inaccurate.  Although the open succeeds, the non-scalar scale factor does trigger failure upon accessing data (due to lazy loading) even without any open file:

```python
import xarray
fn = ""OR_ABI-L1b-RadF-M3C07_G16_s20170732006100_e20170732016478_c20170732016514.nc""
with xarray.open_dataset(fn, engine=""h5netcdf"") as ds:
    print(ds[""Rad""][400, 300])
```

The data file is publicly available at:

s3://noaa-goes16/ABI-L1b-RadF/2017/073/20/OR_ABI-L1b-RadF-M3C07_G16_s20170732006100_e20170732016478_c20170732016514.nc","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-702021297,https://api.github.com/repos/pydata/xarray/issues/4471,702021297,MDEyOklzc3VlQ29tbWVudDcwMjAyMTI5Nw==,500246,2020-10-01T09:47:00Z,2020-10-01T09:47:00Z,CONTRIBUTOR,"However, a simple `xarray.open_dataset(fn, engine=""h5netcdf"") still fails with ValueError only if passed an open file, so there appear to be still other differences apart from the dimensionality of the variable attributes depending on backend.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-702018925,https://api.github.com/repos/pydata/xarray/issues/4471,702018925,MDEyOklzc3VlQ29tbWVudDcwMjAxODkyNQ==,500246,2020-10-01T09:42:35Z,2020-10-01T09:42:35Z,CONTRIBUTOR,"Some further digging shows it's due to differences between the `h5netcdf` and `netcdf4` backends:

```python
import xarray
fn = ""/data/gholl/cache/fogtools/abi/2017/03/14/20/06/7/OR_ABI-L1b-RadF-M3C07_G16_s20170732006100_e20170732016478_c20170732016514.nc""
with xarray.open_dataset(fn, decode_cf=False, mask_and_scale=False, engine=""netcdf4"") as ds:
    print(ds[""esun""].attrs[""_FillValue""])
    print(ds[""Rad""].attrs[""scale_factor""])
with xarray.open_dataset(fn, decode_cf=False, mask_and_scale=False, engine=""h5netcdf"") as ds:
    print(ds[""esun""].attrs[""_FillValue""])
    print(ds[""Rad""].attrs[""scale_factor""])
```

Results in:

```
-999.0
0.001564351
[-999.]
[0.00156435]
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-701973665,https://api.github.com/repos/pydata/xarray/issues/4471,701973665,MDEyOklzc3VlQ29tbWVudDcwMTk3MzY2NQ==,500246,2020-10-01T08:20:20Z,2020-10-01T08:20:20Z,CONTRIBUTOR,"Probably related: when reading an open file through a file system instance, the `_FillValue`, `scale_factor`, and `add_offset` are arrays of length one.  When opening by passing a filename, those are all scalar (as expected):

```python
import xarray
from fsspec.implementations.local import LocalFileSystem
fn = ""/data/gholl/cache/fogtools/abi/2017/03/14/20/06/7/OR_ABI-L1b-RadF-M3C07_G16_s20170732006100_e20170732016478_c20170732016514.nc""
ds1 = xarray.open_dataset(fn, decode_cf=True, mask_and_scale=False)
print(ds1[""esun""].attrs[""_FillValue""])
print(ds1[""Rad""].attrs[""scale_factor""])
with LocalFileSystem().open(fn) as of:
    ds2 = xarray.open_dataset(of, decode_cf=True, mask_and_scale=False)
    print(ds2[""esun""].attrs[""_FillValue""])
    print(ds2[""Rad""].attrs[""scale_factor""])
```

Result:

```
-999.0
0.001564351
[-999.]
[0.00156435]
```

I strongly suspect that this is what causes the `ValueError`, and in any case it also causes downstream problems even if opening succeeds as per the previous comment.","{""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-701948369,https://api.github.com/repos/pydata/xarray/issues/4471,701948369,MDEyOklzc3VlQ29tbWVudDcwMTk0ODM2OQ==,500246,2020-10-01T07:33:11Z,2020-10-01T07:33:11Z,CONTRIBUTOR,"I just tested this with some more combinations:

- `decode_cf=True, mask_and_scale=False`, everything seems fine.
- `decode_cf=False, mask_and_scale=True`, everything seems fine.
- `decode_cf=True, mask_and_scale=True` results in the `ValueError` and associated traceback.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876
https://github.com/pydata/xarray/issues/4471#issuecomment-700696450,https://api.github.com/repos/pydata/xarray/issues/4471,700696450,MDEyOklzc3VlQ29tbWVudDcwMDY5NjQ1MA==,1828519,2020-09-29T13:18:16Z,2020-09-29T13:18:16Z,CONTRIBUTOR,Just tested this with `decode_cf=False` and the rest of the loading process seems fine (note: I used `engine='h5netcdf'` too).,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,710876876