title: How do I find the difference in milliseconds between two datetime objects in Python?
body: <p>I have two datetime objects which are 02:49:01.210000 and 02:49:01.230000:</p>
  
  <pre><code>RA_1 = datetime.datetime.strptime(obs_data['RA'][3], "%H:%M:%S.%f").time()
  RA_2 = datetime.datetime.strptime(pred_data['RA'][3], "%H:%M:%S.%f").time()
  </code></pre>
  
  <p>How do I workout the difference between these two times in milliseconds?</p>
  
  <p>I tried doing RA_1 - RA_2 but got the error:</p>
  
  <pre><code>unsupported operand type(s) for -: 'datetime.time' and 'datetime.time'
  </code></pre>
  
  <p>I also tried using total_seconds() but got the error:</p>
  
  <pre><code>'datetime.time' object has no attribute 'total_seconds'
  </code></pre>