Let function return while other function finishes using threads in Python?

I have a function that modifies data and returns it to the user after modifying. At this point that is the information the user needs so I want to return it ASAP, but I need that modified_data to make calls to an API and upload data it to a DB, but this can be done in the background. Is there a way to have modify_data() return while letting get_more_data() finish?

I tried using threading, but it waits until get_more_data() returns before returning modify_data. I’ve also considered placing both into seprate threads in a parent function but I need modify_data() to generate the data for get_more_data() first.

import threading
def modify_data(data):
    #modify data... example
    modified_data = [item+1 for item in data]
    th = threading.Thread(target=get_more_data(set(modified_data)))
    th.start()
    return modified_data

def get_more_data(data):
    #call api for more data
    #upload to DB

>Solution :

In this line

th = threading.Thread(target=get_more_data(set(modified_data)))

you are executing the get_more_data method to get the target.
Try

th = threading.Thread(target=get_more_data, args=(set(modified_data),))

If you want to learn more about this, take a look here.