信号量代码

import time,random
from multiprocessing import Process,Semaphore
def ktv(i,sem):
    sem.acquire()
    print("{} come in horse".format(i))
    time.sleep(random.randint(1,5))
    print("{} go out horse".format(i))
    sem.release()
if __name__ == '__main__':
    sem = Semaphore(4)
    for i in range(20):
        p = Process(target=ktv,args=(i,sem))
        p.start()