(I noticed that CI wasn't caching anything anyway so I took the liberty of adding it in d3c1730)

There is also https://github.com/meggart/PyYAXArrays.jl which might give some inspiration.

But in the tests it seems to automatically create a lookup of 1:5

Can you show where you mean? NoLookup is always just a Base.OneTo(length) underneath because a Lookup is an AbstractArray and it needs length, so may as well be the indices. That will sometimes display as a 1:5 vector

But this looks really nice to have overall.

Should we also handle/test more complicated lookups like DateTime? And is there information from xarray if a lookup is points or intervals, categorical etc?

Can you show where you mean? NoLookup is always just a Base.OneTo(length) underneath because a Lookup is an AbstractArray and it needs length, so may as well be the indices. That will sometimes display as a 1:5 vector

Ah I'm dumb... the test was checking if the lookup == NoLookup() instead of isa NoLookup.

Should we also handle/test more complicated lookups like DateTime?

Agreed that it'd be useful, but I do not currently have the courage to tackle that hornets nest 😅

And is there information from xarray if a lookup is points or intervals, categorical etc?

No I don't think that kind of information is supported yet according to the docs: https://docs.xarray.dev/en/stable/user-guide/data-structures.html#coordinates
But it may come in the future: pydata/xarray#8463

When reading that page I realized that these conversion methods won't work in two situations:

• Multiple coordinates/lookups assigned to a single dimension.
• Multi-dimensional coordinates/lookups that are assigned to multiple dimensions.

Does DimensionalData support those at all? From the docs I can't figure out how to construct a DimArray for either situation.

When reading that page I realized that these conversion methods won't work in two situations:
Multiple coordinates/lookups assigned to a single dimension.
Multi-dimensional coordinates/lookups that are assigned to multiple dimensions.
Does DimensionalData support those at all? From the docs I can't figure out how to construct a DimArray for either situation.

I'm not sure how common the first would be, or if I understand totally, what's the use case?

The second I have just never implemented but isn't too hard in theory, all the machinery is in place with Transformed lookups we "just" need to swap the functions for matrices. (But it's also very rare in the wild)

My guess is merging this without DateTime handling workingwill lead to a bunch of bug reports. But won't pythoncall just handle that for us? Did you try it?