python3 线程信号量semaphore

# -*- coding: utf-8 -*-
import time
from threading import Thread, Semaphore

def go_ktv(i):
    print("user%s正在....ktv." % (i))
    time.sleep(2)


if __name__ == ‘__main__‘:
    ‘‘‘开启20个线程的运行时间,一个cpu并发执行20个线程,执行时间是最长线程执行的时间‘‘‘
    start_time = time.time()
    p_lst = []
    for i in range(20):
        p = Thread(target=go_ktv, args=(i,))
        p.start()
        p_lst.append(p)
    [pp.join() for pp in p_lst]
    print("运行时间:%s" % (time.time() - start_time))

# user0正在....ktv.
# user1正在....ktv.
# user2正在....ktv.
# user3正在....ktv.
# user4正在....ktv.
# user5正在....ktv.
# user6正在....ktv.
# user7正在....ktv.
# user8正在....ktv.
# user9正在....ktv.
# user10正在....ktv.
# user11正在....ktv.
# user12正在....ktv.
# user13正在....ktv.
# user14正在....ktv.
# user15正在....ktv.
# user16正在....ktv.
# user17正在....ktv.
# user18正在....ktv.
# user19正在....ktv.
# 运行时间:2.0061147212982178

# -*- coding: utf-8 -*-
import time
from threading import Thread, Semaphore

def go_ktv(i):
    sem.acquire()
    print("user%s正在....ktv." % (i))
    time.sleep(2)
    sem.release()


if __name__ == ‘__main__‘:
    ‘‘‘线程加信号量,线程本身是并发执行的,加了信号量,相当于又加了一把互斥锁,并发执行5(信号量大小)个线程‘‘‘
    start_time = time.time()
    sem = Semaphore(5)
    p_lst = []
    for i in range(20):
        p = Thread(target=go_ktv, args=(i,))
        p.start()
        p_lst.append(p)
    [pp.join() for pp in p_lst]
    print("运行时间:%s" % (time.time() - start_time))

# user0正在....ktv.
# user1正在....ktv.
# user2正在....ktv.
# user3正在....ktv.
# user4正在....ktv.
# user5正在....ktv.
# user7正在....ktv.
# user6正在....ktv.
# user8正在....ktv.
# user9正在....ktv.
# user10正在....ktv.
# user12正在....ktv.
# user11正在....ktv.
# user13正在....ktv.
# user14正在....ktv.
# user16正在....ktv.
# user15正在....ktv.
# user17正在....ktv.
# user18正在....ktv.
# user19正在....ktv.
# 运行时间:8.002457857131958