new_contents: import re
  
  def normal():
      a = 'Hello World!'
      print a.replace('World', 'Python')
  
  def viaRegex():
      a = 'Hello World!'
      pattern = re.compile('World')
      print pattern.sub('Python', a)
  
  if __name__ == '__main__':
      normal()
      viaRegex()
  
subject: add python str replace demo