Python multithreading wait till all threads finished

This may have been asked in a similar context but I was unable to find an answer after about 20 minutes of searching, so I will ask.

I have written a Python script (lets say: scriptA.py) and a script (lets say scriptB.py)

In scriptB I want to call scriptA multiple times with different arguments, each time takes about an hour to run, (its a huge script, does lots of stuff.. don't worry about it) and I want to be able to run the scriptA with all the different arguments simultaneously, but I need to wait till ALL of them are done before continuing; my code:

import subprocess

#setup
do_setup()

#run scriptA
subprocess.call(scriptA + argumentsA)
subprocess.call(scriptA + argumentsB)
subprocess.call(scriptA + argumentsC)

#finish
do_finish()

I want to do run all the subprocess.call() at the same time, and then wait till they are all done, how should I do this?

I tried to use threading like the example here:

from threading import Thread
import subprocess

def call_script(args)
    subprocess.call(args)

#run scriptA   
t1 = Thread(target=call_script, args=(scriptA + argumentsA))
t2 = Thread(target=call_script, args=(scriptA + argumentsB))
t3 = Thread(target=call_script, args=(scriptA + argumentsC))
t1.start()
t2.start()
t3.start()

But I do not think this is right.

How do I know they have all finished running before going to my do_finish()?