Pull xarray's nbytes from nbytes attribute on arrays

[maxrjones]

This implements the suggestion in #4842 (comment) to leave the nbytes calculation to the backend array.

Also removed the duplicate docs entry reported in #6565

• ClosesDataArray.nbytes listed twice in API doc block #6565
• Closesnbytes does not return the true size for sparse variables #4842

[maxrjones]

Please let me know if I should add a docstring as suggested in #6565 (comment). I didn't yet because most of the properties do not have docstrings.

[dcherian]

I should add a docstring as suggested

This would be great!

Adding docstrings for the other properties would be a great (separate) PR!

[dcherian]

Thanks @maxrjones can you push any WIP tests you might have for this?

[maxrjones]

Thanks @maxrjones can you push any WIP tests you might have for this?

If it's alright I will wait for #6804 to be merged first because that will greatly simplify testing the changes. After that PR, the following could be added to xarray/tests/test_array_api.py to test both cases:

def test_properties(arrays) -> None:
np_arr, xp_arr = arrays
assert np_arr.nbytes == 48
assert xp_arr.nbytes == 48

[dcherian]

Ah great idea!

[TomNicholas]

Great first contribution @maxrjones ! #6804 should auto-merge in a sec so you can then fetch and merge in main to write your tests 😄

[dcherian]

Thanks @maxrjones I added a sparse variable test that fails on main.

[dcherian]

Thanks @maxrjones This is a great and impactful PR! Welcome to Xarray