title: How to make numpy array column sum up to 1
body: <p>I am working on building a transition matrix for implementing the PageRank algorithm. How could I use numpy to make sure that the columns add up to one.</p>
  
  <p>For example:  </p>
  
  <pre><code>1 1 1   
  1 1 1  
  1 1 1
  </code></pre>
  
  <p>should be normalized to be </p>
  
  <pre><code>.33 .33 .33  
  .33 .33 .33  
  .33 .33 .33
  </code></pre>