title: How to get average from each hour in one week in django?
body: <p>I have a task to get the average some data in each hour inside a week.</p>
  
  <pre><code>{'hour': 0, 'count': 70}
  {'hour': 1, 'count': 92}
  {'hour': 2, 'count': 94}
  {'hour': 3, 'count': 88}
  {'hour': 4, 'count': 68}
  {'hour': 5, 'count': 69}
  {'hour': 6, 'count': 70}
  {'hour': 7, 'count': 82}
  {'hour': 8, 'count': 91}
  {'hour': 9, 'count': 67}
  {'hour': 10, 'count': 92}
  {'hour': 11, 'count': 100}
  {'hour': 12, 'count': 92}
  {'hour': 13, 'count': 55}
  {'hour': 14, 'count': 61}
  {'hour': 15, 'count': 47}
  {'hour': 16, 'count': 36}
  {'hour': 17, 'count': 19}
  {'hour': 18, 'count': 11}
  {'hour': 19, 'count': 6}
  {'hour': 20, 'count': 3}
  {'hour': 21, 'count': 9}
  {'hour': 22, 'count': 27}
  {'hour': 23, 'count': 47}
  </code></pre>
  
  <p>The data above is the result of this query</p>
  
  <pre><code>result = Device.objects.filter(station__in=stations, created_at__range=(start_date, end_date)) \
              .extra({'hour': 'hour(created_at)'}) \
              .values('hour').annotate(count=Count('id')).order_by('hour')
  </code></pre>
  
  <p>the result is queryed by 7 days range, what I want to do is get the average for each hour in 7 days, exampe the total of count in hour 0 is 70 then i need to average it from 7 days.</p>
  
  <p>Any suggestion?</p>