title: Check list and edit second list accordingly
body: <p>I have 3 lists (same shape - about 800 elements), with values being either <strong>1 or 0</strong>. What I want to achieve is a new list that contains the number of <strong>1s in the other 3 lists for that index</strong>.</p>
  
  <p><em>To explain further...</em></p>
  
  <pre><code># I have these
  list1 = [1, 0, 1]
  list2 = [1, 1, 1]
  list3 = [0, 0, 1]
  
  # I want this
  
  new_list = [2, 1, 3]
  </code></pre>
  
  <p>I got this to work by having a nested for loop (i.e: loop through each list and edit the new_list accordingly). However, I was wondering whether there exists a more efficient (especially on memory and resources) approach.</p>