title: How to find the duplicate elements in a list of lists?
body: <p>I got a list of lists and I would like to pick the duplicate elements out of this list of lists and print them. The list of lists is like below,</p>
  
  <pre><code>a = [[0, 1, 2, 3], [4, 5, 6, 375],  [142, 132, 143, 144], [172, 173, 174, 297],  [181, 182, 183, 339], [205, 144, 206, 207], [295, 108, 296, 297]]
  </code></pre>
  
  <p>I tried to use the following script,</p>
  
  <pre><code>for i in range(len(a)):
     for j in range(1, len(a)):
        for m in range(3):
           for n in range(3):
              if a[i][m] == a[j][n]:
                  print a[j][n]
  </code></pre>
  
  <p>but it just print </p>
  
  <pre><code>4
  5
  6
  142
  132
  143
  172
  173
  174
  181
  182
  183
  205
  144
  206
  295
  108
  296    
  </code></pre>
  
  <p>ANY ONE WANT TO TRY AND HELP ME?</p>