title: python sparse matrix get maximum values and index
body: <p>I have a sparse matrix A(equal to 10 * 3 in dense), such as:</p>
  
  <pre><code>print type(A)
  &lt;class scipy.sparse.csr.csr_matrix&gt;
  
  print A
  (0, 0)  0.0160478743808
  (0, 2)  0.0317314165078
  (1, 2)  0.0156596521648
  (1, 0)  0.0575683686558
  (2, 2)  0.0107481166871
  (3, 0)  0.0150580924929
  (3, 2)  0.0297743235876
  (4, 0)  0.0161931803955
  (4, 2)  0.0320187296788
  (5, 2)  0.0106034409766
  (5, 0)  0.0128109177074
  (6, 2)  0.0105766993238
  (6, 0)  0.0127786088452
  (7, 2)  0.00926522256063
  (7, 0)  0.0111941023699
  </code></pre>
  
  <p>The max values for each column is:</p>
  
  <pre><code>print A.max(axis=0)
  (0, 0)  0.0575683686558
  (0, 2)  0.0320187296788
  </code></pre>
  
  <p>I would like to get the <b>index corresponding to the column value</b>.
  I know that the <pre><code>A.getcol(i).tolist()</code></pre> will return me a list of each column which allow me to use argmax() function, but this way is really slow. I am wondering is there any descent way to do?</p>