from threading import Thread, Event
import time

# Code to execute in an independent thread
def countdown(n, started_evt):
    print("countdown starting")
    started_evt.set() 
    while n > 0:
        print("T-minus", n)
        n -= 1
        time.sleep(5)

# Create the event object that will be used to signal startup
started_evt = Event()

# Launch the thread and pass the startup event
print("Launching countdown")
t = Thread(target=countdown, args=(10,started_evt))
t.start()

# Wait for the thread to start
started_evt.wait()
print("countdown is running")