title: AttributeError: 'str' object has no attribute 'sub' Python code
body: <p>Getting this error trying to study for an upcoming final exam and need to understand why it isnt working. Here is the code. </p>
  
  <pre><code>morning_agenda = "At 9.00AM the project team will assemble. The first topic will be fixing the bug in program product.py. We'll break for coffee at 10.30. Work will then continue on improving display.html until 12.30PM."
  
  print morning_agenda
  
  morning_agenda.sub('([0-9]+)\.([0-9]+)', r'\1:\2', morning_agenda)
  
  print morning_agenda
  </code></pre>