title: Using Python, how do I tell if a rectangle and a shape overlap?
body: <p>I'm writing a program in Python.  I have a series of shapes (polygons, defined as a sequence of coordinate pairs) and I need to tell if they overlap a particular rectangle.</p>
  
  <p>Is there an easy algorithm for handling this?  Or, better, is there a pure Python library that can handle these calculations for me?</p>