title: Openpyxl check for empty cell
body: <p><code>openpyxl</code> seems to be a great method for using <em>Python</em> to read <em>Excel</em> files, but I've run into a constant problem. I need to detect whether a cell is empty or not, but can't seem to compare any of the cell properties. I tried casting as a string and using <code>""</code> but that didn't work. The type of cell when it is empty is <code>None</code>, or <code>NoneType</code> but I can't figure out how to compare an object to that. </p>
  
  <p>Suggestions? I understand <code>openpyxl</code> is under development, but maybe this is more a general <em>Python</em> problem.</p>