title: Why float numbers (when typed in shell) has an additional digits (zeros)
body: <p>I'm new in python and I was typing float numbers in python2.7 shell when I figured this:</p>
  
  <pre><code>&gt;&gt;&gt; 9.9
  9.9000000000000004
  &gt;&gt;&gt; 9.9==_
  True
  &gt;&gt;&gt; 9.9==9.90000004
  False
  &gt;&gt;&gt; 7.7
  7.7000000000000002
  &gt;&gt;&gt; 7.7==_
  True
  &gt;&gt;&gt; 7.7==7.700000002
  False
  </code></pre>
  
  <p>my question is, why does 9.9 became 9.900000000000004? Is it default? </p>
  
  <p>Please let me know if this is a duplicate. thanks.</p>