title: Python to convert everything to lowercase after a pattern
body: <p>I have a file that contains the following format. everything is seperated by <code>;</code> but the actual article is seperated by <code>;;;</code>.</p>
  <pre><code>audio.wav;2869.52;2870.55;;;Maar dishierdie Mense
  audio1.wav;2925.32;2926.77;;;van die Padwerkers Wat
  </code></pre>
  <p>How do I lowercase everything after <code>;;;</code> so the output file is</p>
  <pre><code>audio.wav;2869.52;2870.55;;;maar dishierdie mense
  audio1.wav;2925.32;2926.77;;;van die padwerkers wat
  </code></pre>
  <p>So far I have</p>
  <pre><code>import re
  
  with open(filename, 'r') as txtfile:
          data = txtfile.read()
          re.sub(r&quot;&quot;, lambda m: m.group().lower(), data)
  
  </code></pre>