title: using the python threading.timer to execute the callback function and kill the previous function
body: <p>Here is the code : </p>
  
  <pre><code>import threading
  import time
  
  def fun_01() :
      timer = threading.Timer(3,call_back)
  
      print("start~")
  
      timer.start()
  
      #If the call_back function is executed after 3 seconds,
      # the fun_01 function must be terminated (before 10 seconds have elapsed)
      print("waiting")
      time.sleep(5)
      print("end wait")
  
  
      print("Hello~")
  
      return "exit"
  
  def call_back():
      print("call_back")
      return "end"
  
  print(fun_01())
  </code></pre>
  
  <p><strong>If the call_back function is executed after 3 seconds,
     the fun_01 function must be terminated (before 10 seconds have elapsed)
    .......help me</strong></p>