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
427410885,MDU6SXNzdWU0Mjc0MTA4ODU=,2857,Quadratic slowdown when saving multiple datasets to the same h5 file (h5netcdf),2418513,closed,0,,,24,2019-03-31T15:47:40Z,2022-01-12T07:19:06Z,2022-01-12T07:19:06Z,NONE,,,,"I can't quite understand what's wrong with my side of the code, wondering if this kind of slowdown is expected or not?

Basically, what I'm doing is something like this:

```python
with h5py.File('file.h5', 'w') as f:
    f.flush()  # reset the file
for i, ds in enumerate(datasets):
    ds.to_netcdf('file.h5', group=str(i), engine='h5netcdf', mode='a')
```

And here's the log for saving 20 datasets, the listed times are for each dataset independently. Instead of the expected 10 sec (which is already kind of slow, but whatever), I get 2 minutes. The time to save each dataset seems to increase linearly, which leads to a quadratic overall slowdown:

```
saving dataset... 00:00:00.559135
saving dataset... 00:00:00.924617
saving dataset... 00:00:01.351670
saving dataset... 00:00:01.818111
saving dataset... 00:00:02.356307
saving dataset... 00:00:02.971077
saving dataset... 00:00:03.685565
saving dataset... 00:00:04.375104
saving dataset... 00:00:04.575837
saving dataset... 00:00:05.179975
saving dataset... 00:00:05.793876
saving dataset... 00:00:06.517916
saving dataset... 00:00:07.190257
saving dataset... 00:00:07.993795
saving dataset... 00:00:08.786421
saving dataset... 00:00:09.414821
saving dataset... 00:00:10.729006
saving dataset... 00:00:11.584044
saving dataset... 00:00:14.160655
saving dataset... 00:00:14.460564

CPU times: user 1min 49s, sys: 12.8 s, total: 2min 2s
Wall time: 2min 4s
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2857/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
423749397,MDU6SXNzdWU0MjM3NDkzOTc=,2836,xarray.concat() with compat='identical' fails for DataArray attrs,2418513,open,0,,,9,2019-03-21T14:11:29Z,2021-07-08T17:42:52Z,,NONE,,,,"Not sure if it was ever supposed to work with numpy arrays, but it actually does :thinking::

```python
>>> attr = np.array([[3, 4]])
>>> d1 = xr.Dataset({'z': 1}, attrs={'y': attr})
>>> d2 = xr.Dataset({'z': 2}, attrs={'y': attr.copy()})
>>> xr.concat([d1, d2], dim='z', compat='identical')
```

However, it fails if you use DataArray attrs:

```python
>>> attr = xr.DataArray([3, 4], {'x': [1, 2]}, 'x')
>>> d1 = xr.Dataset({'z': 1}, attrs={'y': attr})
>>> d2 = xr.Dataset({'z': 2}, attrs={'y': attr.copy()})
>>> xr.concat([d1, d2], dim='z', compat='identical')
ValueError: The truth value of an array with more than one element is ambiguous. 
Use a.any() or a.all()
```

Given that the check is simply `(a is b) or (a == b)`, should it try to do something smarter for array-like attrs?","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2836/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
423016453,MDU6SXNzdWU0MjMwMTY0NTM=,2824,Dataset.from_records()?,2418513,open,0,,,4,2019-03-20T00:46:19Z,2021-05-13T20:20:52Z,,NONE,,,,"Currently, to easily create a `Dataset` from an existing numpy recarray (not a `DataArray`, which is currently bugged anyway with recarrays due to #1434), I couldn't find an easier way than

```python
df = xr.Dataset.from_dataframe(pd.DataFrame(my_recarray).set_index('foo'))
```

(which is kind of dumb since it allocates the memory twice)

It would definitely be nice to be able to do just this (perhaps with extra arguments to set index on the fly etc):

```python
df = xr.Dataset.from_records(my_recarray, ...)
```

(Apologies if I'm missing something obvious.)","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2824/reactions"", ""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
549712566,MDU6SXNzdWU1NDk3MTI1NjY=,3695,mypy --strict fails on scripts/packages depending on xarray; __all__ required,2418513,closed,0,6213168,,3,2020-01-14T17:27:44Z,2020-01-17T20:42:25Z,2020-01-17T20:42:25Z,NONE,,,,"Checked this with both 0.14.1 and master branch.

Create `foo.py`:

```python
from xarray import DataArray
```

and run:

```sh
$ mypy --strict foo.py
```

which results in

```
foo.py:1: error: Module 'xarray' has no attribute 'DataArray'
Found 1 error in 1 file (checked 1 source file)
```

I did a bit of digging trying to make it work, it looks like what makes the above script work with mypy is adding

```python
__all__ = ('DataArray',)
```

to `xarray/__init__.py`, otherwise mypy treats those imports as ""private"" (and is correct in doing so).

Should `__all__` be added to the root `__init__.py`? To any `__init__.py` in subpackages as well?","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3695/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
423774214,MDU6SXNzdWU0MjM3NzQyMTQ=,2837,DataArray plotting: pyplot compat and passing the style,2418513,open,0,,,6,2019-03-21T14:57:12Z,2019-04-11T16:25:49Z,,NONE,,,,"These are two unrelated issues in one really that I've noticed while trying to plot things directly from DataArray objects.

----

The following works as expected, by converting DataArray to pandas first)

```python
>>> arr.to_series().plot(style='.-')
>>> arr.to_series().plot.line(style='.-')
```

Passing Series to pyplot.plot() directly also works and retains index:

```python
>>> plt.plot(arr.to_series(), '.-')
```

Trying to set style directly when plotting from DataArray doesn't work:
```python
>>> arr.plot(style='.-')
AttributeError: Unknown property style
>>> arr.plot.line(style='.-')
AttributeError: Unknown property style
```

Passing DataArray to pyplot.plot() loses index:

```python
>>> plt.plot(arr, '.-')
# works but loses coords; same as plot.plot(arr.values, '.-')
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2837/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
423023519,MDU6SXNzdWU0MjMwMjM1MTk=,2825,KeyError on selecting empty time slice from a datetime-indexed Dataset,2418513,open,0,,,4,2019-03-20T01:21:56Z,2019-03-20T17:58:24Z,,NONE,,,,"(xarray version: 0.11.3)

Just wanted to confirm this is expected behaviour: `sel()` with a date that would yield an empty selection throws an exception (I would naturally expect it to return a zero-length dataarray/dataset instead):

```python
>>> foo = xr.DataArray(
    np.array([1, 2, 3]),
    {'t': pd.to_datetime(['2018-01-01', '2018-02-02T01:01', '2018-02-02T02:02'])},
    dims=['t']
)

>>> foo.sel(t='2018-01-01').size
1

>>> foo.sel(t='2018-02-02').size
2

>>> foo.sel(t='2018-03-03').size  # expected 0?

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
TypeError: an integer is required

During handling of the above exception, another exception occurred:

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine._date_check_type()
KeyError: '2018-03-03'

During handling of the above exception, another exception occurred:

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
TypeError: an integer is required

During handling of the above exception, another exception occurred:

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine._date_check_type()

KeyError: '2018-03-03'

During handling of the above exception, another exception occurred:

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
KeyError: 1520035200000000000

During handling of the above exception, another exception occurred:

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
KeyError: Timestamp('2018-03-03 00:00:00')

During handling of the above exception, another exception occurred:

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
KeyError: 1520035200000000000

During handling of the above exception, another exception occurred:

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()
KeyError: Timestamp('2018-03-03 00:00:00')

...

```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2825/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue