title: Python override __str__ outside of class definition
body: <p>Say I have a module that I've imported that works fine but doesn't provide a good <code>__str__</code> method and I want to add one.</p>
  
  <p>In some hybrid language:</p>
  
  <pre><code>from foo import Foo
  
  Foo.prototype._str__ = function myNIcePrintFunction(){
  
  }
  </code></pre>
  
  <p>How do I do this please in Python please?</p>