title: Pandas DataFrame use Timedelta to set time in H:M:S:f format to 00:00:00:000
body: <p>I have a pandas DataFrame with the following column <code>(first column = index)</code>:</p>
  <pre><code>0         14:43:45:921
  
  1         14:43:45:923
  
  2         14:43:45:925
  </code></pre>
  <p>I would like to modify this column, or add another column with the time starting at <code>0</code>:</p>
  <pre><code>0         00:00:00.000
  
  1         00:00:00.002
  
  2         00:00:00.004
  </code></pre>
  <p>So far, I've tried the following code:</p>
  <pre><code>df['time'].apply(pd.Timedelta)
  </code></pre>
  <p>This is giving me the following error:</p>
  <pre><code>expected hh:mm:ss format
  </code></pre>
  <p>To me, the problem is</p>
  <p>a) convert the time format <code>HH:MM:SS:fff</code> to <code>HH:MM:SS.fff</code> and</p>
  <p>b) get the <code>timedelta</code> function to work.</p>
  <p>Does anyone have any suggestions? Thanks!</p>