title: Rounding in jinja2 brackets
body: <p>I guess just generally I'm curious about what operations are allowable in jinja2 brackets, e.g. what I'm trying to do is perform an operation on embedded data like so:</p>
  
  <pre><code>{{ round(255*(mileage['chevy'] - mileage['ford']))/1000 }}
  </code></pre>
  
  <p>This throws the error on traceback: </p>
  
  <blockquote>
    <p>UndefinedError: 'round' is undefined</p>
  </blockquote>
  
  <p>Similarly when I try to use 'abs' in a bracketed jinja block, I get an Undefined error--even though they're both standard lib functions. Is there some way to perform this operation during template-rendering, rather than before passing the data?</p>