Python creates multiple threads (join thread synchronization)

import threading
import time

def timer(v):       #定时器线程函数
    print(v)
    
def demo(x,y):
    for i in range(x,y):
        print(i,end=" ")
    time.sleep(5)      #线程挂起5秒    
    
t=threading.Timer(2,timer,args=(1,))     #2秒后执行定时器
t2=threading.Timer(0.5,timer,args=(2,))      #0.5秒后执行定时器
t.start()
t2.start()

threading.stack_size(1024*64)
print("当前线程栈大小：",threading.stack_size())
print("活动线程：",threading.active_count())
print("当前线程对象：",threading.current_thread())
print("枚举所有线程：",threading.enumerate())

t2.cancel()     #取消线程

t3=threading.Thread(target=demo,args=(1,10))
t3.start()
t3.join(3)      #等待线程3秒后，执行后面代码
print("t3 is alive?",t3.is_alive())
t4=threading.Thread(target=demo,args=(11,20))
t4.start()