title: Python precision in string formatting with float numbers
body: <p>I don't understand why, by formatting a string containing a float value, the precision of this last one is not respected. Ie:</p>
  
  <pre><code>'%f' % 38.2551994324
  </code></pre>
  
  <p>returns:</p>
  
  <pre><code>'38.255199'
  </code></pre>
  
  <p>(4 signs lost!)</p>
  
  <p>At the moment I solved specifying:</p>
  
  <pre><code>'%.10f' % 38.2551994324
  </code></pre>
  
  <p>which returns '38.2551994324' as expected… but should I really force manually how many decimal numbers I want? Is there a way to simply tell to python to keep all of them?! (what should I do for example if I don't know how many decimals my number has?)</p>