title: How to change a function's return using a decorator?
body: <p>I want create a decorator to change a function's return value like that, How to do that like below?:</p>
  
  <pre><code>def dec(func):
      def wrapper():
          #some code...
          #change return value append 'c':3
      return wrapper
  
  @dec
  def foo():
      return {'a':1, 'b':2}
  
  result = foo()
  print result
  {'a':1, 'b':2, 'c':3}
  </code></pre>