イベント

import logging
import threading
import time

logging.basicConfig(level=logging.DEBUG, format='%(threadName)s: %(message)s')


def worker1(event):
    event.wait()  #event.set()が呼び出されるまで待機
    logging.debug('start')
    time.sleep(3)
    logging.debug('end')


def worker2(event):
    event.wait()  #event.set()が呼び出されるまで待機
    logging.debug('start')
    time.sleep(3)
    logging.debug('end')


def worker3(event):
    logging.debug('start')
    time.sleep(3)
    logging.debug('end')
    event.set()

if __name__ == '__main__':
    event = threading.Event()
    t1 = threading.Thread(target=worker1, args=(event,))
    t2 = threading.Thread(target=worker2, args=(event,))
    t3 = threading.Thread(target=worker3, args=(event,))
    t1.start()
    t2.start()
    t3.start()

Thread-3: start
Thread-3: end
Thread-1: start
Thread-2: start
Thread-1: end
Thread-2: end