title: Extend python build-in class: float
body: <p>I would like to change the </p>
  
  <pre><code>float.__str__ 
  </code></pre>
  
  <p>function of the build in float type (python 2)</p>
  
  <p>I tried to extend this class.</p>
  
  <pre><code>class SuperFloat(float):
      def __str__(self):
          return 'I am' + self.__repr__()
  </code></pre>
  
  <p>However, when I add it it becomes a normal float</p>
  
  <pre><code>egg = SuperFloat(5)
  type(egg+egg)
  </code></pre>
  
  <p>returns float</p>
  
  <p>My ultimate goal is that also</p>
  
  <pre><code>egg += 5
  </code></pre>
  
  <p>stays a superfloat</p>