event 实现两个程序的交互

event.wait() 等待一定时间，或者当遇到event.set() 时，继续执行 

event.clear() 清除信号 

event.set() 设置信号 

event.isset() 判断信号 

例一： 红绿灯

#event 实现两个线程之间的交互
import time, threading

def lighter():
    if not event.is_set():
      event.set()
    count = 0
    while True:
      if count<10:
         print('the green light is run %s'%count)
      elif count<15:

         print('the yellow light is run %s'%count)

      elif count<20:
          print('the red light is run %s'%count)
          event.clear()

      else:
          count = 0
          event.set()
      time.sleep(1)
      count += 1

def cars(n):
    while True:
      if event.is_set():
          print('%s is running'%n)


      else:
          print('%s is stoping'%n)

      time.sleep(1)

event = threading.Event()
light = threading.Thread(target=lighter, args=())
light.start()
car = threading.Thread(target=cars, args=('tesl', ))
car.start()


例二 开关门 

import threading, time, random


def door():
    door_count_number = 0
    while True:
        if door_state.is_set():
            print('the door is open')
            door_count_number += 1

        else:
            print('the door has been closed')
            door_count_number = 0
            door_state.wait()

        if door_count_number > 3:
            door_state.clear()

        time.sleep(0.5)



def staff(n):
    print('%s is comming'%n)
    while True:
      if door_state.is_set():
        print('%s is pass'%n)
        break
      else :
        door_state.set()
        print('staff[%s]sees door got closed, swipped the card')

      time.sleep(0.5)


door_state = threading.Event()
Door = threading.Thread(target=door)
Door.start()

for i in range(5):
    p = threading.Thread(target=staff, args=(i, ))
    time.sleep(random.randrange(3))
    p.start()