title: Find the sum of subsets of a list in python
body: <p>This is probably very simple and I'm overlooking something...</p>
  
  <p>I have a long list of integers, in this case representing daily visitors to a website.  I want a new list of <em>weekly</em> visitors.  So I need to get groups of seven from the original list, sum them, and add them to a new list.</p>
  
  <p>My solution seems pretty brute force, inelegant:</p>
  
  <pre><code>numweeks = len(daily) / 7
  weekly = []
  for x in range(numweeks):
      y = x*7
      weekly.append(sum(visitors[y:y+7]))
  </code></pre>
  
  <p>Is there a more efficient, or more pythonic way of doing this?</p>