title: 2 names for a same attribute
body: <p>I would like to know if there is a way to "link" two attributes of a class or to give 2 names to a same attribute? </p>
  
  <p>For example, I'm actually working on a script which create triangle from data given by users. My triangle is ABC. Sides of this triangle are AB, BC and CA. So the triangle has got these 3 attributes (self.AB, self.BC, self.CA). But AB = BA so I would like to allow users to do <code>print myInstance.BA</code> instead of <code>print myInstance.AB</code>. </p>
  
  <p>So I thought to create the attribute self.AB and the property BA (which return self.AB). That work fine when I try to do <code>print myInstance.BA</code> instead of <code>print myInstance.AB</code> but I'm greedy... </p>
  
  <p>I also would like to allow users to do <code>myInstance.BA = 5</code> instead of <code>myInstance.AB = 5</code> and when doing this also edit the attribute AB.</p>
  
  <p>Is there is a way to do this ?</p>