同步条件Event

'''同步条件Event'''
import threading
import time

class Boss(threading.Thread):
   def run(self):
      print('Boss:今晚大家加班到23:00！')
      print(event.isSet()) # False
      event.set() # ②设置event状态值为True，所有阻塞线程被激活等待操作系统调度
      time.sleep(3)
      print('Boss:22:30大家可以提前下班了！')
      event.set() # ⑤再次将event值设为True
      # print(event.isSet())

class Worker(threading.Thread):
   def run(self):
      event.wait() # ①一开始本应先运行这5个线程，但event.isSet()为False，所以将被阻塞
      print('Worker:哎，又加班，烦死了！')
      time.sleep(1)
      event.clear() # ③event.clear()将event的状态值恢复为False
      event.wait() # ④又被阻塞
      print('Worker:卧槽，终于下班了，大家冲啊！')

if __name__ == '__main__':
   event = threading.Event() # 生成event对象
   threads = []

   for i in range(5):
      threads.append(Worker())
   threads.append(Boss())

   for t in threads:
      t.start()

   for t in threads:
      t.join()

   print('ending...')
'''
event.isSet():返回event的状态值
event.wait():如果event.isSet()==False将阻塞线程
event.set():设置event的状态值为True，所有阻塞池的线程激活进入就绪状态，等待操作系统调度
event.clear():恢复event的状态值为False
'''
# An event is a simple synchronization object;the event represents an internal flag,事件是一个简单的同步对象；事件代表一个内部标志
# and threads can wait for the flag to be set, or set or clear the flag themselves.并且线程可以等待标志被设置，或者自己设置或清除标志
# If the flag is set, the wait method doesn’t do anything.如果设置了标志，wait方法不会做任何事情
# If the flag is cleared, wait will block until it becomes set again.如果标志被清除，wait将阻塞，直到它再次被设置
# Any number of threads may wait for the same event.任意数量的线程都可以等待同一个事件