title: How do you measure the size of a cgi.FieldStorage instance?
body: <p>When a file is uploaded, the standard way of representing it is <code>cgi.FieldStorage</code> (at least Pyramid does it that way). However, if I want to know the length in an efficient way, how do I get it? For example:</p>
  
  <pre><code>uploaded = cgi.FieldStorage()
  </code></pre>
  
  <p>If this variable now came from a request, how to determine the file's size?</p>