title: python 2d array to dict
body: <p>I want to create a dict from lower triangle of a symmetric matrix represented as 2d array. For examples if the numpy array is;</p>
  
  <pre><code>array([[0, 2, 3],
         [2, 0, 4],
         [3, 4, 0]])
  </code></pre>
  
  <p>then I want the dict to look like;</p>
  
  <pre><code>{('1', '0'): 2, ('2', '0'): 3, ('2', '1'): 4}
  </code></pre>
  
  <p>There is a similar post for vector;</p>
  
  <p><a href="https://stackoverflow.com/questions/877578/fastest-way-to-convert-a-numpy-array-into-a-sparse-dictionary">Fastest way to convert a Numpy array into a sparse dictionary?</a></p>
  
  <p>I am relatively new to python so any help/suggestoins appreciated.</p>