线程数量问题

import time,random
from threading import Thread
import threading
def sing():
    for i in range(3):
        print("唱第%d首歌"%(i))
        time.sleep(random.random())
def dance():
    for i in range(3):
        print("跳第%d段舞"%(i))
        time.sleep(random.random())

if __name__ == '__main__':
    t1=Thread(target=sing,)
    t2=Thread(target=dance,)

    t1.start()
    t2.start()
    while True:
        count=len(threading.enumerate())  #threading.enumerate()查看线程数量
        print("线程个数：",count)
        if count==1:
            break
    # 注意：至少得有一个主线程

 

 

线程实现的第二种方式

from threading import Thread

class MyThread(Thread):
    def __init__(self,url):
        Thread.__init__(self)
        self.url=url
    def run(self):
        print("线程的业务逻辑代码写在这里！")
if __name__ == '__main__':
    url="http://img.netbian.com/file/2019/0311/small91c78151d9fe112e49d322fab157abd11552278397.jpg",
    t=MyThread(url)
    t.start()

#多线程的执行顺序是不一定的