title: Python: lists and copy of them
body: <p>I can not explain the following behaviour:</p>
  
  <pre><code>l1 = [1, 2, 3, 4]
  l1[:][0] = 888
  print(l1) # [1, 2, 3, 4]
  l1[:] = [9, 8, 7, 6]
  print(l1) # [9, 8, 7, 6]
  </code></pre>
  
  <p>It seems to be that <code>l1[:][0]</code> refers to a copy, whereas <code>l1[:]</code> refers to the object itself.</p>