title: Numpy float64 vs Python float
body: <p>I'm battling some floating point problems in Pandas read_csv function.  In my investigation, I found this:</p>
  
  <pre><code>In [15]: a = 5.9975
  
  In [16]: a
  Out[16]: 5.9975
  
  In [17]: np.float64(a)
  Out[17]: 5.9974999999999996
  </code></pre>
  
  <p>Why is builtin <code>float</code> of Python and the <code>np.float64</code> type from Python giving different results?  I thought they were both C++ doubles?</p>