I did more tries today, and still no luck. Here is what I did.
I have a out7.usda file and I imported it into Houdini through menu. It could be imported successfully and here is the parm for the file printed from Python Shell:
>>> out7 = hou.node('/obj/out7')
>>> out7.evalParm('out7/file')
'D

TechSupport/USD/USD_build_Hou17.5/out7.usda'
So, I tried to set up such a parm in another usd file, out8.usda, to load it up, but I couldn't find the ‘out7/file’ parm. Please see the pictures.
As you can see, for node out8, there is no equivalent parm named ‘out8’ like ‘out7’ for out7.
So next I tried to add such a parm but failed:
>>> out8.setParms({'out8/file':'D

TechSupport/USD/USD_build_Hou17.5/usd8.usda'})
Traceback (most recent call last):
File “<console>”, line 1, in <module>
File “C

PROGRA~1/SIDEEF~1/HOUDIN~1.173/houdini/python2.7libs\houpythonportion\Nod
e.py”, line 235, in setParms
raise hou.OperationFailed(“Invalid parameter name: ” + parm_name)
OperationFailed: The attempted operation failed.
Invalid parameter name: out8/file
I know this is a rude manner and it's normal that it failed. But can anyone please tell me how could I do it correctly?
Thank you!