title: Grasping the basics of in-place operations
body: <p>So... </p>
  
  <pre><code>a = [2,3,4,5]
  
  for x in a:
    x += 1
  
  a = [2,3,4,5]
  </code></pre>
  
  <p>Nada. </p>
  
  <p>but if I ...</p>
  
  <pre><code>a[2] += 1
  a = [2,3,5,5]
  </code></pre>
  
  <p>Clearly my mind fails to comprehend the basics. <code>print(x)</code> returns only the integer within the cell so it should simply add the one automatically for each list cell. What's the solution and what am I not grasping? </p>