title: Asynchronous call with a callback function in python and callback should exit on anyone respone
body: <p>I am in learning face and I need to call 2 external APIs but don't want to wait for response which means asyc call. whenever I get the 1st response from those APIs it should call one of my callback function and it should not capture the response from another API, means it should call only once time based on the response I am getting first. How should I achieve this? Below is the task-</p>
  
  <pre><code>def callback_function(response):
      pass #do some action here
  
  def test_async():
      print 'some'
      print 'some2'
      request.post('api1', payload) # this should call my callback 
      request.post('api2', payload) # this should call my callback
      print 'some3'
      print 'some4'
      return 1
  </code></pre>