title: python float formatting weirdness?
body: <p>I'm trying to debug two different python scripts that execute very similar code.  These scripts set    <code>a</code>, which is a simple float.  </p>
  
  <p>For script 1:</p>
  
  <pre><code>ipdb&gt; print sys.version
  2.7 (r27:82500, Jul 15 2010, 13:04:38)
  [GCC 4.1.2 20071124 (Red Hat 4.1.2-42)]
  ipdb&gt; type(a)
  &lt;type 'float'&gt;
  ipdb&gt; print a
  17.23105
  ipdb&gt; print '{0:.4f}'.format(a)
  17.2311
  </code></pre>
  
  <p>For script 2: </p>
  
  <pre><code>ipdb&gt; print sys.version
  2.7 (r27:82500, Jul 15 2010, 13:04:38)
  ipdb&gt; print type(a)
  &lt;type 'float'&gt;
  ipdb&gt; print a
  17.23105
  ipdb&gt; print '{0:.4f}'.format(a)
  17.2310
  </code></pre>
  
  <p>How is it possible that <code>a</code> formats differently in the two cases?  In what ways can <code>a</code> possibly differ between the two scripts, if I've already checked that their value is the same at <code>17.23105</code> ?  (unfortunately the python code that originally sets <code>a</code> is very, very long... I wouldn't want to bore everyone with 1000+ lines)</p>