title: Distance outside shapely.Polygon
body: <p>How do I establish the distance a point is from a polygon? If the point is within the polygon the result should be 0.</p>
  
  <p>I'm guessing something like:</p>
  
  <pre><code>def distance_from(poly,point):
    if poly.contains(point): return 0 
    return poly.exterior.distance(point)
  </code></pre>