title: Create list of lists filled with the same values
body: <p>I'm trying to create a list containing multiple lists filled with the same values this way:</p>
  
  <p><code>l1 = [[False] * n] * m</code></p>
  
  <p>There are no any errors and at first glance it looks like valid lists of lists (<code>print(l1) for n=m=3 : [[False,False,False],[False,False,False],[False,False,False]]</code>)</p>
  
  <p>But when I tried <code>l1[0][0] = True</code> I got a strange behaviour - list has turned into <code>[[True,False,False],[True,False,False],[True,False,False]]</code>.</p>
  
  <p>So, why did such list initialization results to it? And what should I do to create a list properly?</p>