old_contents: #!/usr/bin/env python
  # -*- coding:utf-8 -*-
  from __future__ import division
  from __future__ import unicode_literals
  from __future__ import print_function
  
  class Queue(object):
      def __init__(self):
          self.items = []
  
      def isEmpty(self):
          return len(self.items)) == 0
  
      def enqueue(self, item):
          self.items.insert(0, item)
  
      def dequeue(self):
          return self.items.pop()
  
      def size(self):
          return len(self.items)
  
new_contents: #!/usr/bin/env python
  # -*- coding:utf-8 -*-
  from __future__ import division
  from __future__ import unicode_literals
  from __future__ import print_function
  
  class Queue(object):
      def __init__(self):
          self.items = []
  
      def isEmpty(self):
          return len(self.items) == 0
  
      def enqueue(self, item):
          self.items.append(item)
  
      def dequeue(self):
          return self.items.pop(0)
  
      def size(self):
          return len(self.items)
  
subject: improve queue implementation