title: How to use numpy to add any two elements in an array and produce a matrix?
body: <p>The native python codes are like this:</p>
  
  <pre><code>&gt;&gt;&gt; a=[1,2,3,4,5,6]
  &gt;&gt;&gt; [[i+j for i in a] for j in a]
  [[2, 3, 4, 5, 6, 7], 
   [3, 4, 5, 6, 7, 8], 
   [4, 5, 6, 7, 8, 9], 
   [5, 6, 7, 8, 9, 10], 
   [6, 7, 8, 9, 10, 11], 
   [7, 8, 9, 10, 11, 12]]
  </code></pre>
  
  <p>However, I have to use numpy to do this job as the array is very large.
  Does anyone have ideas about how to do the same work in <strong>numpy</strong>?</p>