groupby repr

[dcherian]

Adds a simple groupby repr. Feedback appreciated

da = xr.DataArray(
    np.random.randn(10, 20, 6),
    dims=["x", "y", "z"],
    coords={"z": ["a", "b", "c", "a", "b", "c"], 
            "x": [1, 1, 1, 2, 2, 3, 4, 5, 3, 4]},
)

DataArrayGroupBy, grouped over 'x' 
5 groups with labels 1, 2, 3, 4, 5

DataArrayGroupBy, grouped over 'y' 
20 groups with labels 0, 1, 2, 3, 4, 5, ..., 15, 16, 17, 18, 19

da.groupby("z")
DataArrayGroupBy, grouped over 'z' 
6 groups with labels 'a', 'b', 'c', 'd', 'e', 'f'

• Tests added
• Passes black . && mypy . && flake8
• Fully documented, including whats-new.rst for all changes and api.rst for new API

[dcherian]

formatting._get_indexer_at_least_n_items returns a tuple so I unpack it here. This could alternatively be an if condition in formatting.first_n_items and formatting.last_n_items but I felt this might be cleaner. I guess we could isntead call np.array(self.values)[key]

[max-sixty]

Big improvement! Thanks!
(I don't have any strong views on the implementation, looks fine, but others may have more context)

[dcherian]

Thanks @max-sixty , test failure is unrelated.

[dcherian]

I'll merge in a couple of days if no one else has comments.

[max-sixty]

Thanks @dcherian !

I think these are the sorts of moderate code changes that make the library much easier for newer users (and existing ones!)

[dcherian]

You're welcome :)