title: Read number from file and put it into two-dimensional list
body: <p>I am new to Python. My file contains these numbers:</p>
  
  <pre><code>2,3
  4,5
  7,8
  -4,3
  </code></pre>
  
  <p>How can I read this file and convert it into a two dimensional list so that I can calculate an area?</p>