title: Numpy average function rounding off error
body: <p>I find this very weird.  Can someone tell me whats going on here?</p>
  
  <pre><code>&gt;&gt;&gt;a = [1,0,1]
  &gt;&gt;&gt;np.mean(a)
     0.66666666666666663
  &gt;&gt;&gt;2.0/3
     0.6666666666666666
  </code></pre>
  
  <p>What's up with the 3 in the end of the output of <code>np.mean(a)</code>? Why isn't it a 6 like the line below it or a 7(when rounding off)?</p>