python Events
Events事件
Events是一个简单的同步对象，
事件表示一个内部标志和线程
可以等待设置标志，或设置或清除标志本身。
Events使用
生成event对象
event = threading.Event()
设置标志位
event.set()
清空标志位
event.clear()
等待设置标志位 如果标志位没有设置就一直等待
event.wait()
如果设置了标记，等待方法什么也不做。
如果标记被清除，等待将阻塞，直到它再次被设置。
任何数量的线程都可以等待相同的事件。
标志位被设定，代表绿灯，直接通行。
标志位被清空，代表红灯，wait等待变绿灯。等待标志位在设定。
通过Event来实现两个或多个线程间的交互，下面是一个红绿灯的例子，即起动一个线程做交通指挥灯，生成几个线程做车辆，车辆行驶按红灯停，绿灯行的规则。
import threading
import time
event = threading.Event()
def lighter():
count = 0
event.set() # 变绿灯
while True:
if count >5 and count < 10 : #改红灯
event.clear() #清空标志位
print("\033[41;1mred light is on...\033[0m")
elif count >10:
event.set() # 变绿灯
count = 0
else:
print("\033[42;1mgreen light is on...\033[0m")
event.set() # 变绿灯
time.sleep(1)
count+=1
def car(name):
while True:
if event.is_set(): #代表绿灯
print("[%s] runing..."% name)
time.sleep(1)
else:
print("[%s] sees red light,waiting..."% name)
event.wait()
print("[%s] green light is on,start going...")
light = threading.Thread(target=lighter,)
light.start()
car1 = threading.Thread(target=car,args=("Tesla",))
car1.start()
运行结果：
1 green light is on... 2 [Tesla] runing... 3 green light is on... 4 [Tesla] runing... 5 [Tesla] runing... 6 green light is on... 7 [Tesla] runing... 8 green light is on... 9 green light is on... 10 [Tesla] runing... 11 green light is on... 12 [Tesla] runing... 13 [Tesla] runing... 14 red light is on... 15 [Tesla] sees red light,waiting... 16 red light is on... 17 red light is on... 18 red light is on... 19 green light is on... 20 [%s] green light is on,start going... 21 [Tesla] runing... 22 [Tesla] runing... 23 green light is on... 24 [Tesla] runing... 25 green light is on... 26 [Tesla] runing... 27 green light is on... 28 [Tesla] runing... 29 [Tesla] runing... 30 green light is on... 31 green light is on... 32 [Tesla] runing... 33 [Tesla] runing... 34 red light is on... 35 [Tesla] sees red light,waiting...
