Rewrite excitondb.py

[palful]

The class excitondb.py is too complicated and convoluted, especially in the plotting part. I find all the plotting functions very difficult to follow.

I think it should be:
(i) rewritten for clarity
(ii) the plotting stuff separated in a different class
(iii) better commented what is happening inside the function and what is the logic

[rreho]

Hi,
related to this issue. I don't understand why in excitondb we have certain loops involving the kvc bands and others kcv. I believe kvc is the correct one now. Can you confirm @palful ?

https://github.com/yambo-code/yambopy/blob/7658a05b2e6ca4cc2bdf9077f001f07868481680/yambopy/dbs/excitondb.py#L670C1-L671C35

Regarding rewriting excitondb I have some ideas in mind and I could do that. However, it might be beneficial to add pytests for the core outputs of the YamboExcitonDB class. I can take care of those simple tests such as IO, generation of core attributes and observables.

[palful]

Hi Riccardo,

Yes it should be kvc!

As for the rewriting, the most important thing is that much of the plotting stuff is convoluted, redundant and not very flexible. This will also be affected by an upcoming patch changing how pathfinding in k-space works for plotting, which will likely impact the BandStructure object and the interpolating functions which are called inside this class. I am waiting for this patch to be ready in order to understand better how the impact will be.

But it is clear that most of the plotting stuff can be moved away, for example in a dedicated file inside yambopy/bse.

I totally agree about adding basic tests. The important thing is also that when we touch this class, we must be absolutely sure that the core plotting functionalities work as intended, i.e., the tutorial scripts (however modified) keep working for the users.

[rreho]

Perfect. I agree with your comments, and I am looking forward to this upcoming patch.
I'll keep the class as it is for now then and prepare basic tests. In this way, once the patch arrives, we can double-check.