new_contents: def example_1():
      text = 'yeah, but no, but yeah, but no, but yeah'
  
      print(text.replace('yeah', 'yep'))
  
  
  def example_2():
      text = 'Today is 11/27/2012. PyCon starts 3/13/2013'
  
      import re
      print(re.sub(r'(\d+)/(\d+)/(\d+)', r'\3-\1-\2', text))
  
  
  def example_3():
      text = 'Today is 11/27/2012. PyCon starts 3/13/2013'
  
      import re
      date_pattern = re.compile(r'(\d+)/(\d+)/(\d+)')
      print(date_pattern.sub(r'\3-\1-\2', text))
  
  
  def example_4():
      text = 'Today is 11/27/2012. PyCon starts 3/13/2013'
  
      import re
      date_pattern = re.compile(r'(\d+)/(\d+)/(\d+)')
      newtext, n = date_pattern.subn(r'\3-\1-\2', text)
      print(newtext)
      print(n)
  
  
  if __name__ == '__main__':
      example_1()
      print(75 * '-') 
  
      example_2()
      print(75 * '-')
  
      example_3()
      print(75 * '-')
  
      example_4()
      print(75 * '-')
  
subject: add code samples for recipe 2.5