title: TypeError: unhashable type: 'numpy.ndarray'
body: <p>From a text file containing three columns of data I want to be able to just take a <code>slice</code> of data from all three columns where the values in the first column are equal to the values defined in <code>above</code>. I then want to put the slice of data into a new array called <code>slice</code> (I am using <strong>Python 2.7</strong>)</p>
  
  <pre><code>above = range(18000, 18060, 5)
  
  data = np.loadtxt(open('data.txt'), delimiter=None)
  
  energies = (np.hsplit(data, 3))[0]
  
  slice = set(energies)&amp;set(above)
  </code></pre>
  
  <p>The above comes back with:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;pyshell#27&gt;", line 1, in &lt;module&gt;
      set(energies)&amp;set(above)
  TypeError: unhashable type: 'numpy.ndarray
  </code></pre>