Hi, Sakit.
It's as Zico says. You can't "re-run setup.py", it's not supported and may result in broken instance; it will not reset it for sure. If you need a lot of settings to be reset to what they were right after first run of setup.py, you will have to reinstall it. Then I would create a backup of that fresh instance so you could always "fall back" to it to revert your changes (good for trying and learning things).