title: Mapping two arrays containing strings to the same integer values
body: <p>I have 2 arrays like:</p>
  
  <pre><code>['16.37.235.200','17.37.235.200','16.37.235.200', '18.37.235.200']
  ['17.37.235.200','17.37.235.200','16.37.235.200', '17.37.235.200']
  </code></pre>
  
  <p>And I want to map (injective) every IP address to an integer value.<br>
  Like for that instance above, eg.:</p>
  
  <pre><code>[0,1,0,3]
  [1,1,0,1] 
  </code></pre>
  
  <p>Is their an existing function (of NumPy or anything else) for that?</p>