title: print python stack trace without exception being raised
body: <p>Something is happening with one of my class's instance variables. I want to make the variable a property, and whenever it is accessed I want to print out the stack trace of all the code leading up to that point, so I can see where it's being messed with. How do I print out the stack trace when no exception has been raised? I know if there is an exception I can do something like <code>traceback.format_tb(sys.exc_info()[2])</code>.</p>
  
  <p>Also what might be useful is to print only the last 3-4 levels, since the first few are probably not going to be that interesting.</p>