title: How Python calculate number?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/286061/python-decimal-place-issues-with-floats">python - decimal place issues with floats</a>  </p>
  </blockquote>
  
  <p>In [4]: 52+121.2 </p>
  
  <p>Out[4]: 173.19999999999999 </p>