title: Changing lists in Python
body: <pre><code>#Case 1
  myList=[1,2,3,4]
  old=myList
  myList=[5,6,7,8]
  print(old)
  
  #Case 2
  myList=[1,2,3,4]
  old=myList
  myList[0]=10
  print(old)
  
  #Case 3
  myList=[1,2,3,4]
  old=myList.copy()
  myList[0]=10
  print(old)
  
  [1, 2, 3, 4]
  [10, 2, 3, 4]
  [1, 2, 3, 4]
  </code></pre>
  
  <p>For me the case 3 is the safe case and Case 2 is clear. However, I am not able to clearly understand why in case 1 <code>old</code> is not changed.</p>