Relative path setting for loading data python script

How to set relative path for loading Data using scripts in python slicer?

Relative to what? Please be more specific.

There are paths in the object, such as

You can concatenate the relative path to one of these.

(See below a response that a user posted a few hours ago. Unfortunately, the response was flagged as spam - probably due to reviving a stale discussion and posting a short answer with a suspicious link - and I’ve made a mistake of confirming that this was a spam.)

PYTHONPATH is used by the python interpreter to determine which modules to load.

PATH is used by the shell to determine which executables to run.