title: In Pandas, how to convert a string to a datetime object with milliseconds?
body: <p>I have a column of event's timestamp in my dataframe, looks like "2016-06-10 18:58:25:675", the last 3 digits are milliseconds, is there a efficient way to transform this column to a Pandas datatime type?</p>
  
  <p>When I try: </p>
  
  <pre><code>pd.to_datetime('2016-06-10 18:57:35:317')
  </code></pre>
  
  <p>An error occurs saying "Unknown string format".</p>