Hi,
So I get that syntax differs a bit in python parm expressions vs scripts or pythonSOP but I am a bit stumped on this one. I have a scripts I use to automate alembic and Collada imports. One particular function is to filter the contents of collada geo type nodes and any of those nodes that are visible or not. A simple exmaple would be along the lines of :

for node in hou.selectedNodes():
if node.type().name() == ‘geo’:
new_name = ‘Mesh_’ + str(node)
node.setName(new_name, 1)

I am appending names say in this example of geo type nodes so that I merge various sets in another node using object_merge nodes. So, in this example, I would set the objmerge parm to a wildcard ‘Mesh_*’ and so import the various geo meshes I want.

It works fine but it would be super convenient if instead I could set a longer function expression as a python parm instead to filter the merge elements. I haven't been able to work that out though as an expression. Is it possible? Say, to set a python parm expression that in pseudo code will do this?
i.e.,

for nodes in nodes:
if node.type.name = ‘geo’
if node.isVisible():
merge node

So far, I have been working along the lines of using my existing scripts to put the filtered objects into a list and then set the parm expression to a space separated line of string object names with their paths. Obviously though, that is kinda hard coded at the time it is run. I wonder if there is a way for the parm to evaluate the merge filters itself using functions directly (instead of just setting the parm merge field to a string like ‘/obj/object/Mesh1 /obj/object/Mesh2 /obj/object/Mesh3 /obj/object/Mesh4’ etc. or ‘Mesh*’)

Thanks!

you can do anything you want in python, just make sure your expression results in space separated list of paths or patterns

to pull in all displayed objects from /obj level except for objects with object merge using the expression (to avoid recursion) you can use expression like this in your path:


just be aware that such expression will update only when Object Merge is cooked again, not necessarily immediately as you change display of the objects or add new object