多线程等待

import  threading,time

def run():
    time.sleep(3)
    print('哈哈哈')

start_time=time.time()
threads=[] #存放启动的5个线程
for i in range(5):
    t = threading.Thread(target=run)
    t.start()
    threads.append(t)
print('threads',threads)
    # t.join()  #主线程等待子线程执行结束

for t in threads:  #主线程循环等待5个子线程执行结束
    t.join() #循环等待,等待5个线程都结束

end_time=time.time()
run_time=end_time-start_time
print('run_time..',run_time)