title: Count the frequency of a recurring list -- inside a list of lists
body: <p>I have a list of lists in python and I need to find how many times each sub-list has occurred. Here is a sample,</p>
  
  <pre><code>from collections import Counter
  list1 = [[ 1., 4., 2.5], [ 1., 2.66666667, 1.33333333], 
           [ 1., 2., 2.], [ 1., 2.66666667, 1.33333333], [ 1., 4., 2.5],
           [ 1., 2.66666667, 1.33333333]]   
  c = Counter(x for x in iter(list1))
  print c
  </code></pre>
  
  <p>I above code will work, if the elements of the list were hashable (say int), but in this case they are lists and I get an error</p>
  
  <pre><code>TypeError: unhashable type: 'list'
  </code></pre>
  
  <p>How can I count these lists so I get something like</p>
  
  <pre><code>[ 1., 2.66666667, 1.33333333], 3
  [ 1., 4., 2.5], 2
  [ 1., 2., 2.], 1
  </code></pre>