title: Sum all list-elements to new list
body: <p>I have an old list and I want to sum up every single element to a new list:</p>
  
  <pre><code>    lst_old = [1, 2, 3, 4, 5]
      lst_new = [1, 3, 6, 10, 15]
  </code></pre>
  
  <p>Is there an elegant way to implement that in Python 3 with short and fast code? Apart from <code>sum()</code> which only prints last element I couldn't find a proper solution for my problem.</p>