title: NumPy's savetxt does not export delimiter when defining fmt for each column
body: <p>So I have an array called <code>final</code>, that gets saved to text with a header. The array is built with numpy.column_stack as follows:</p>
  
  <pre><code>numpy.column_stack((SampNo, dummy, data, data1))
  </code></pre>
  
  <p>When I use</p>
  
  <pre><code>numpy.savetxt(f, final, delimiter=',', fmt='%1.7f')
  </code></pre>
  
  <p>The text file is saved with the delimiter correctly. However, I need the first two columns to be string rather than float, and when I use:</p>
  
  <pre><code>numpy.savetxt(f, final, delimiter=',', fmt='%s %s %1.7f %1.7f')
  </code></pre>
  
  <p>...the comma delimiter no longer appears in the file.</p>
  
  <p>Also, as an aside, I end up using <code>%1.7f</code> 8 times after the two <code>%s</code> options as there are 10 columns in total. Is there a neater way to do this?</p>