Unit aware manipulation?

[durack1]

This newly announced pint package sounds interesting. Not sure if it's more useable than udunits?

[pochedls]

This looks cool, @durack1. I think if there is a feature / use-case in mind, this could be migrated to: #271.

[lee1043]

I also just came across with the pint-xarray which I think is cool. Some example usage can be found here. I copied and pasted below use case from their website. It automatically assign proper units after variables are multiplied. It returns error when user tries addiction/subtraction of variables in different units -- which could be cool, but at the same time it could be annoying if user intended.

import xarray as xr
import cf_xarray.units
import pint_xarray

ds = xr.open_dataset('gs://cmip6/CMIP6/CMIP/NCAR/CESM2-FV2/historical/r2i1p1f1/Amon/sfcWind/gn/v20200226/', engine='zarr')
ds = ds.pint.quantify()

squared_wind = ds['sfcWind'] ** 2
squared_wind.pint.units

Out:
<Unit('meter ** 2 / second ** 2')>

[jypeter]

Unfortunately, this example does not mention the original units... According to the sfcWind entry in the CMIP6 DR, I would expect: m s-1

The squared units should therefore be m2 s-2 if we want a really useful result

[jypeter]

BTW, is it possible to update units of xarray objects by directly assigning a string? e.g. one of the following? That's something I regularly did with cdms2 objects

squared_wind.pint.units = 'm2 s-2'
squared_wind.units = 'm2 s-2'

It's probably possible to do so for an in-memory variable. But what about changing the units (or any other attribute) of a variable in a nc file. My apologies for this slightly off-topic question

With cdms2, I would open the file in 'r+' mode, use a file variable pointer, assign the new units and close the file.