python-实现双端队列

# encoding=utf-8

class DoubleQueue(object):
    """双端队列"""
    def __init__(self):
        self.__items = []

    def is_empty(self):
        """判空"""
        return self.__items == []

    def add_front(self, item):
        """在队头添加元素"""
        self.__items.insert(0, item)

    def add_rear(self, item):
        """在队尾添加元素"""
        self.__items.append(item)

    def remove_front(self):
        """从队头删除元素"""
        return self.__items.pop(0)

    def remove_rear(self):
        """从队尾删除元素"""
        return self.__items.pop()

    def size(self):
        """返回队列大小"""
        return len(self.__items)