title: Python TypeError: 'numpy.int32' object is not iterable
body: <p>I am trying to take the entropy of my k-means result dataframe and I am getting the error back: TypeError: 'numpy.int32' object is not iterable
  I dont understand why. </p>
  
  <pre><code>from collections import Counter 
  def calcEntropy(x):
      p, lens = Counter(x), np.float(len(x))
      return -np.sum(count/lens*np.log2(count/lens) for count in p.values())
  k_means_sp['entropy']=[calcEntropy(x) for x in k_means_sp['cluster']]
  </code></pre>
  
  <p>and then I get the error message:</p>
  
  <pre><code>&lt;ipython-input-26-d375ecf00330&gt; in &lt;module&gt;()
  ----&gt; 1 k_means_sp['entropy']=[calcEntropy(x) for x in k_means_sp['cluster']]
  
  &lt;ipython-input-26-d375ecf00330&gt; in &lt;listcomp&gt;(.0)
  ----&gt; 1 k_means_sp['entropy']=[calcEntropy(x) for x in k_means_sp['cluster']]
  
  &lt;ipython-input-23-f5508ea8782c&gt; in calcEntropy(x)
        1 from collections import Counter
        2 def calcEntropy(x):
  ----&gt; 3     p, lens = Counter(x), np.float(len(x))
        4     return -np.sum(count/lens*np.log2(count/lens) for count in p.values())
  
  /Users/mpiercy/anaconda/lib/python3.6/collections/__init__.py in __init__(*args, **kwds)
      535             raise TypeError('expected at most 1 arguments, got %d' % len(args))
      536         super(Counter, self).__init__()
  --&gt; 537         self.update(*args, **kwds)
      538 
      539     def __missing__(self, key):
  
  /Users/mpiercy/anaconda/lib/python3.6/collections/__init__.py in update(*args, **kwds)
      622                     super(Counter, self).update(iterable) # fast path when counter is empty
      623             else:
  --&gt; 624                 _count_elements(self, iterable)
      625         if kwds:
      626             self.update(kwds)
  
  TypeError: 'numpy.int32' object is not iterable
  
  k_means_sp.head()
  
        credit    debit   cluster
  0   9.207673    8.198884    1
  1   4.248495    8.202181    0
  2   8.149668    7.735145    2
  3   5.138677    7.859741    0
  4   8.058163    7.918614    2
  </code></pre>