title: Using Python to count the number of layers in a AutoCAD file
body: <p>I've created a <code>GUI</code> using <code>PyQt5</code> wich takes <code>shapefiles</code> and one <code>.dwg</code> file as inputs.
  In the <code>.dwg</code> file, I have a certain amount of standard <code>layers</code> that should be inside.
  If one or more of those <code>layers</code> is missing, I would like to be able to inform the user which <code>layers</code> are missing.</p>
  
  <p>For example, if the <code>.dwg</code> files must have these <code>layers</code> ('Trees', Roads', 'Houses', 'Lakes' etc.), if 'Roads' is missing, I would like the user to be inform when he launches the <code>GUI</code>.</p>
  
  <p>Using Python I have to use a Python extension/library I guess. But I've looked and <code>PyAcad</code> or <code>PythonCAD</code> don't seem to be very implemented yet.
  If anyone has used Python for AutoCAD, I am looking for some advice/tips.
  And if you have an alternative idea for my problem that would be greatly appreciated !</p>