Is there a way in python to evaluate an attribute (in this case P) given a prim and a uv coordinate?
I'm guessing yes but have trouble finding a function that seems to do it….

I believe there are functions for that type of lookup on hou.Face or hou.Surface, depending on your geometry type.

they only seem to be available for curves, i.e you can only specify “u”

Unless it's undocumented?

How lovely. Given the state of HOM it wouldn't surprise me if the documentation was wrong, though that functionality is probably just missing. You might want to submit a support question to be sure though…

Edit: These are the closest I could find, but I see what you mean.

surface: attribValueAt [sidefx.com]

face: attribValueAt [sidefx.com]

VEX and Expressions have primUV() so you might want to consider those languages if possible.

But I agree that HOM is still in a pretty early state! Fingers crossed that they will implement more functions soon

Yes I hope it gets some more love soon. They got so far with it, it's not missing much. But with VEX improving that does help, just not in this instance. I'll just have to roll my own function.