• [x] User visible changes (including notable bug fixes) are documented in whats-new.rst
• [ ] New functions/methods are listed in api.rst

This makes many arguments keyword-only, except for dim to avoid da.weighted(...).mean("lat", "lon") (i.e. da.weighted(...).mean(dim="lat", skipna="lon")) which silently does the wrong thing. I am sure I forgot some and for some I was unsure so I left them as is.

Question: do we want an deprecation cycle? Currently it just errors for da.weighted(...).mean("dim", True). Might be nice to do it, however, @dcherian if I am not mistaken you did this without a deprecation in #5950, e.g. for da.mean etc.?

python import numpy as np import xarray as xr air = xr.tutorial.open_dataset("air_temperature") wgt = np.cos(np.deg2rad(air.lat)) air.weighted(wgt).mean("lat", "lon")

• [x] Closes #6092
• [x] Passes pre-commit run --all-files
• [x] User visible changes (including notable bug fixes) are documented in whats-new.rst

One change is that it is no longer possible to compare to a string, i.e. version.parse(xr.__version__) < "0.20.0" errors.

As mentioned in #6092 there are 3 options - if there is a preference I am happy to update this PR.

```python from distutils.version import LooseVersion from packaging import version

LooseVersion(xr.version) version.parse(xr.version) version.Version(xr.version)

currently:

if LooseVersion(mod.version) < LooseVersion(minversion): pass

options:

if version.parse(mod.version) < version.parse(minversion): pass

if version.Version(mod.version) < version.Version(minversion): pass

if Version(mod.version) < Version(minversion): pass ```

This PR renames the da and ds fixtures (to da_fixture and ds_fixture) and moves them to conftest.py. This allows to remove the flake8 error suppression for the tests and seems more how the fixtures are intended to be used (from the pytest side). I think the name changes makes it a bit more obvious what happens but moving them to may make it a bit less obvious (if you don't know where to look).

Removing the flake8 error ignores also unearthed some unused imports:

https://github.com/pydata/xarray/blob/787a96c15161c9025182291b672b3d3c5548a6c7/setup.cfg#L155-L156

(What I actually wanted to do is move the tests for rolling to it's own file - but I think it makes sense to do this first.)

• [x] Closes #2007
• [ ] Tests added (for all bug fixes or enhancements)
• [ ] Tests passed (for all non-documentation changes)
• [ ] Fully documented, including whats-new.rst for all changes and api.rst for new API

Ok, this was easier to do than initially thought, we can use np.pad(a, pads, mode='wrap') in nputils.rolling_window. However, I'm not sure if that is enough already<sup>*</sup>.

I added an initial test, but could use some pointers where else you want this to be tested.

Questions: * is fill_value='periodic' a good api? * should the fill_value keyvalue be ported to rolling? * should this also be mentioned in the docs for rolling (I only learned about rolling.construct yesterday)

<sup>*</sup>rolling is present incore/dataset.py, core/dataarray.py, core/variable.py, core/rolling.py, core/dask_array_ops.py, core/nputils.py, core/ops.py, core/common.py, core/missing.py, and core/duck_array_ops.py that can be a bit daunting...

• [x] Closes #3263, potentially part of #4671

It's worth a try.