text: import threading
  import asyncio
  
  
  @asyncio.coroutine
  def hello():
      print('hello world! (%s)' % threading.current_thread())
      yield from asyncio.sleep(1)
      print('Hello again! (%s)' % threading.current_thread())
  
  
  loop = asyncio.get_event_loop()
  tasks = [hello(), hello()]
  loop.run_until_complete(asyncio.wait(tasks))    # 两个coroutine是由同一个线程并发执行的
  loop.close()
  