import threading, time
 def run(n):
     print("task", n)
     time.sleep(2)
 
 t1 = threading.Thread(target=run, args=("t1",))
 t2 = threading.Thread(target=run, args=("t2",))
 t1.start()
 t2.start()
 run("t1")
 run("t2")
 
 import threading, time
 class MyThread(threading.Thread):
     def __init__(self, n):
         super(MyThread, self).__init__()
         self.n = n
     def run(self):
         print("running task", self.n)
         time.sleep(2)
 t1 = MyThread("t1")
 t2 = MyThread("t2")
 
 t1.run()
 t2.run()
 t1.start()
 t2.start()
 
 import threading, time
 def run(n):
     print("task", n)
     time.sleep(2)
     print("task done", n, threading.current_thread())  # 打印子线程
 
 start_time = time.time()
 t_objs = []
 for i in range(50):
     t = threading.Thread(target=run, args=("t %s" % i,))
     t.start()
     t_objs.append(t)  # 把每个线程实例都加进来 不阻塞后面线程的启动
 for t in t_objs:  # 取列表里的每个线程
     t.join()  # 等待并行的每个线程全都执行完毕 在往下走
 
 print("----all threads has finished...", threading.current_thread(), threading.active_count())  # 打印主线程，程序默认有一个主线程
 print("cost:", time.time() - start_time)  # threading.active_count()活跃线程个数  import time,threading
 
 import time,threading
 class MyThread(threading.Thread):
     def __init__(self, n, sleep_time):
         super(MyThread, self).__init__()
         self.n = n
         self.sleep_time = sleep_time
 
     def run(self):
         print("running task", self.n)
         time.sleep(self.sleep_time)
         print("task done", self.n)
 
 
 t1 = MyThread("t1", 2)  # 等待2秒
 t2 = MyThread("t2", 4)  # 等待4秒
 t1.start()
 t2.start()
 t1.join()  # wait() 等待t1线程执行完再往下走 程序进程变成串行了 主程序卡主了
 t2.join()  # t1执行完之后等t2 等待t2 执行完之后再往下走
 print("main threading....")
 # 程序末尾有一个默认的join 守护线程
 
 import threading, time
 def run(n):
     print("task", n)
     time.sleep(2)
     print("task done", n, threading.current_thread())  # 打印子线程 如果不设置为守护线程，那么程序会执行到这里
 start_time = time.time()
 t_objs = []
 for i in range(50):
     t = threading.Thread(target=run, args=("t %s" % i,))
     t.setDaemon(True)  # 设置为守护线程 设置为守护线程之后，主线程执行完之后程序就退出了，不管守护线程有没有执行完都会退出
     t.start()
     t_objs.append(t)  # 把每个线程实例都加进来 不阻塞后面线程的启动
 # for t in t_objs: #取列表里的每个线程
 #    t.join() #等待并行的每个线程全都执行完毕 在往下走
 
 print("----all threads has finished...")
 print("cost:", time.time() - start_time)