title: How to format in numpy savetxt such that zeros are saved only as "0"
body: <p>I am saving a <code>numpy</code> sparse array (densed) into a csv. The result is I have a 3GB csv. The problem is 95% of the cells are 0.0000. I used <code>fmt='%5.4f'</code>. How can I format and save such that the zeros are saved only as 0 and the non zero floats are saved with the <code>'%5.4f'</code> format ? I am sure I can get the 3GB down to 300MB if I can do this.</p>
  
  <p>I am using </p>
  
  <pre><code>np.savetxt('foo.csv', arrayDense, fmt='%5.4f', delimiter = ',')
  </code></pre>
  
  <p>Thanks
  Regards</p>