title: Count number of events per hour in a time-serie - Python
body: <p>I have this date-time attribute from which i want to create its appropriate time series counting the number of  events per hour : </p>
  
  <pre><code>ID  Date-time
  1   31/12/2017 22:55
  2   31/12/2017 22:27
  3   31/12/2017 22:17
  4   31/12/2017 21:55
  5   31/12/2017 20:48
  6   31/12/2017 11:03
  7   31/12/2017 09:58
  8   31/12/2017 09:52
  9   31/12/2017 09:16
  10  31/12/2017 08:11
  </code></pre>
  
  <p>I want to obtain  : </p>
  
  <pre><code>ID  Date-time        Events
  1   31/12/2017 22:00,3
  2   31/12/2017 21:00,1
  3   31/12/2017 20:00,1
  4   31/12/2017 19:00,0
  5   31/12/2017 18:00,0
  6   31/12/2017 17:00,0
  7   31/12/2017 16:00,0
  8   31/12/2017 15:00,0
  9   31/12/2017 14:00,0
  10  31/12/2017 13:00,0
  11  31/12/2017 12:00,0
  12  31/12/2017 11:00,0
  13  31/12/2017 10:00,0
  14  31/12/2017 09:00,3
  15  31/12/2017 08:00,1
  </code></pre>
  
  <p>Is there a simple way to perform this task in Python ?</p>
  
  <p>Lionel</p>