title: Accessing sparse matrix elements
body: <p>I have a very large sparse matrix of the type 'scipy.sparse.coo.coo_matrix'. I can convert to csr with .tocsr(), however .todense() will not work since the array is too large. I want to be able to extract elements from the matrix as I would do with a regular array, so that I may pass row elements to a function.</p>
  
  <p>For reference, when printed, the matrix looks as follows:</p>
  
  <pre><code>(7, 0)  0.531519363001
  (48, 24)    0.400946334437
  (70, 6) 0.684460955022
  ...
  </code></pre>