title: Can a format string be specified to call .lower()?
body: <p>When I specify a format string I'd like to make it call <code>.lower()</code> probably as part of the <a href="https://docs.python.org/2/library/string.html#grammar-token-conversion" rel="nofollow"><code>conversion</code></a> step:</p>
  
  <pre><code># before:
  "Bring out the holy {name!s}".format(name="RaBbIt")
  # 'Bring out the holy RaBbIt'
  
  # after:
  "Bring out the holy {name!s.lower()}".format(name="RaBbIt")
  # 'Bring out the holy rabbit'
  </code></pre>
  
  <p>I'll pass this format string to another class and I cannot alter how it uses it that's why I have no way to call <code>.lower()</code> inside the <code>.format()</code> call.</p>
  
  <p>Can somehow the conversion to lowercase be specified in the format string?</p>