title: Rounding to significant figures in numpy
body: <p>I've tried searching this and can't find a satisfactory answer.</p>
  
  <p>I want to take a list/array of numbers and round them all to n significant figures. I have written a function to do this, but I was wondering if there is a standard method for this? I've searched but can't find it. Example:</p>
  
  <pre><code>In:  [  0.0, -1.2366e22, 1.2544444e-15, 0.001222 ], n=2
  Out: [ 0.00, -1.24e22,        1.25e-15,  1.22e-3 ]
  </code></pre>
  
  <p>Thanks</p>