You can create new envirohnment and call your function with new env, it will not affect any thing front end.

Below is the code for create new Env-

new_env = odoo.api.Environment(self.cr, self.uid, self.context)

Define your object with new Env like below-

partner_obj = new_env['res.partner']

Then you can call any partner_object function which will not block your UI.

You can see many examples in odoo base addons.

You can use threading technique. It will run the process in background and UI will not be blocked.

eg:-

import threading

def fn(self):

threaded_calculation = threading.Thread(target=YOUR_FN_NAME)
threaded_calculation.start()