hou.Parm Object not available in simple shelf script?

[Krion 6]

Hi guys,

I have this simple script in a Shelf tool:

import hou

selectednodes = hou.selectedNodes()

for selectednode in selectednodes:

    parms = selectednode.parms()
    for parm in parms:

        val = parm.eval()

        if type(val) is int or type(val) is float:
            parm.setExpression('ch(chsop("ref_source"')

But it gives an error when trying to execute (on the line that it's getting the 'val' variable). 

    return _hou.Parm_eval(self)
hou.ObjectWasDeleted: Attempt to access an object that no longer exists in Houdini.

 

Why is this? I have done this sortof stuff before. This is something that is possible right?

Thanks in advance.

[Krion 6]

Now after trying again the same code, it doesn't give the error anymore, but Houdini just crashes unless I comment-out the parm.setExpression().

Weird. I don't see what I'm doing wrong.

 

This the crash log:

 

Edited November 2, 2021 by Krion

[Krion 6]

I see the issue is mainly on nodes with multiparms,

which is precisely the kind of node for which I am writing this script..