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/pull/2330#issuecomment-422458598,https://api.github.com/repos/pydata/xarray/issues/2330,422458598,MDEyOklzc3VlQ29tbWVudDQyMjQ1ODU5OA==,1217238,2018-09-18T16:23:00Z,2018-09-18T16:23:00Z,MEMBER,"Sorry for taking so long here.

I'm still not entirely comfortable with this change -- it adds some additional complexity to the `Dataset` constructor that seems unnecessary. There's no inherit reason why calling a constructor on an object of the same type needs to work. If anything, I would like to deprecate/remove this behavior on `DataArray` (e.g., in favor of using a more explicit call to `DataArray.copy(data=new_data)`).

> To answer your question though, we hit this when inheriting from a Dataset: the object is initialized with a dataset, which is super-ed up to the Dataset constructor

If I understand this correctly, you've written something like:
```python
class MyDataset(xarray.Dataset):
    def __init__(self, dataset):
        super().__init__(dataset)
```

Is there any reason why you couldn't just write:
```python
class MyDataset(xarray.Dataset):
    def __init__(self, dataset):
        super().__init__(dataset.data_vars, dataset.coords, dataset.attrs)
```

> I think we should do something here, rather than change behavior by coincidence.

I don't think it's *quite* a coincidence here -- we are changing the behavior of `Dataset.__iter__`/`Dataset.keys()`, and this is a logical consequence of interpreting a Dataset as a mapping of its data variables :).","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,346294369
https://github.com/pydata/xarray/pull/2330#issuecomment-411258309,https://api.github.com/repos/pydata/xarray/issues/2330,411258309,MDEyOklzc3VlQ29tbWVudDQxMTI1ODMwOQ==,1217238,2018-08-08T01:56:04Z,2018-08-08T01:56:04Z,MEMBER,"Now I'm having second thoughts. It does make me a little nervous to add special cases that distinguish between `xr.Dataset(ds, coords=some_coords)` and `xr.Dataset(ds.data_vars, coords=some_coords)`.

Maybe my proposed solution above is too complex, and it would be better simply to default the `coords` and `attrs` argument to those arguments from a passed Dataset object. This is basically what we do for DataArray.

That said, I do think we should try to resist the notion that every class constructor must also work for coercion to that class. This tends to result in a slightly confused interface. A separate `as_dataset()` function (even in user code) could give exactly the desired result in only be a few lines of code.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,346294369
https://github.com/pydata/xarray/pull/2330#issuecomment-410046100,https://api.github.com/repos/pydata/xarray/issues/2330,410046100,MDEyOklzc3VlQ29tbWVudDQxMDA0NjEwMA==,1217238,2018-08-02T19:46:57Z,2018-08-02T19:46:57Z,MEMBER,"> An alternative approach - more friendly but less explicit - is for any other argument (coords, attrs) supplied to overwrite the Dataset's

I think this would be slightly preferred, and also more consistent with the model of a Dataset as only iterating over `data_vars`. This suggests that at the very least, `Dataset(ds)` and `Dataset(ds.data_vars)` should be consistent after we finish the changes described in https://github.com/pydata/xarray/issues/884. Note that `ds.data_vars` will pull in coordinates associated with the DataArray objects.

To be more precise, I would probably make:
```
ds2 = Dataset(ds1, coords, attrs)
```
equivalent to
```
ds2 = ds1.copy()
ds2.coords.update(coords)
ds2.attrs.update(attrs)
```","{""total_count"": 2, ""+1"": 2, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,346294369