title: How to create polygons with arcs in shapely (or a better library)
body: <p>I am trying to use shapely to identify the area used by a shape and the area used by the tools that will cut it on a CNC router. The shape is imported from a dxf drawing using <a href="https://pypi.python.org/pypi/ezdxf/0.6.2" rel="noreferrer">ezdxf</a>.</p>
  
  <p>The tool paths can be either rectangles (if they are cut by a saw disk that follows a straight line) or a set of segments (if they are routed by a milling bit). In both cases I can use a <a href="http://toblerity.org/shapely/shapely.geometry.html#shapely.geometry.base.BaseGeometry.buffer" rel="noreferrer">LineString.buffer()</a> to automatically create the offsets and find the area used by the tool.</p>
  
  <p>I am using shapely because I think it is the best tool available to find out if shapes overlap each other (using <a href="http://toblerity.org/shapely/shapely.geometry.html#shapely.geometry.base.BaseGeometry.union" rel="noreferrer"><code>union()</code></a> to merge all the tools into one shape and <a href="http://toblerity.org/shapely/shapely.geometry.html#shapely.geometry.base.BaseGeometry.overlaps" rel="noreferrer"><code>overlaps()</code></a> to find the interference). Please let me know if there is a better tool for this purpose.</p>
  
  <p><code>buffer()</code> does a good job at creating segments to represent arcs on the corners.</p>
  
  <p>Is there a way to create the segments to represent arcs on the shape itself?</p>
  
  <p>For example, how do I create the arc on the left of this shape? Do I need to create my own (slow) python function? Or is there an optimized shapely way?</p>
  
  <p><img src="https://i.stack.imgur.com/mmulD.png" alt="Green is the part, yellow are the saw disk cuts, magenta are the milling bit cuts"></p>