Python execute playsound in separate thread

Use threading library :

from threading import Thread
T = Thread(target=playy) # create thread
T.start() # Launch created thread

You may not have to worry about using a thread. You can simply call playsound as follows:

def playy():  
    playsound('beep.mp3', block = False)

This will allow the program to keep running without waiting for the sound play to finish.