new_contents: #!/usr/bin/env python
  # encoding: utf-8
  
  """Initializing a defaultdict.
  """
  
  import collections
  
  
  def default_factory():
      return 'default value'
  
  
  d = collections.defaultdict(default_factory, foo='bar')
  print 'd:', d
  print 'foo =>', d['foo']
  print 'bar =>', d['bar']
  print 'empty =>', d.get('empty')
  
subject: add defaultdict