round_print.py

from threading import Event, Thread

event1 = Event()
event2 = Event()
event3 = Event()
i = 0


def f1():
  global i
  while True:
    event1.wait()
    print("t1", i)
    i += 1
    event2.set()
    event1.clear()


def f2():
  global i
  while True:
    event2.wait()
    print("t2", i)
    i += 1
    event3.set()
    event2.clear()


def f3():
  global i
  while True:
    event3.wait()
    print("t3", i)
    i += 1
    event1.set()
    event3.clear()


if __name__ == '__main__':
  t1 = Thread(target=f1)
  t1.start()
  t2 = Thread(target=f2)
  t2.start()
  t3 = Thread(target=f3)
  t3.start()
  event1.set()
  t1.join()
  t2.join()
  t3.join()