title: Python rounding error with simple sum
body: <pre><code>&gt;&gt;&gt; sum([0.3, 0.1, 0.2])
  0.6000000000000001
  
  &gt;&gt;&gt; sum([0.3, 0.1, 0.2]) == 0.6
  False
  </code></pre>
  
  <p>What can I do to make the result be exactly 0.6? 
  I don't want to round the result to a certain number of decimal digits because then I could lose precision for other list instances.</p>