python核心编程-标准类型派生-可变类型

#!/usr/bin/env python# -*- coding: UTF-8 -*-class SortedKeyDict(dict):    def keys(self):        return sorted(super(SortedKeyDict, self).keys())d = SortedKeyDict((('zheng-cai', 67), ('hui-jun', 68),('xin-yi', 2)))print 'By iterator:'.ljust(12), [key for key in d]print 'By keys():'.ljust(12), d.keys()

输出：

D:\Python27\test>object06.pyBy iterator: ['zheng-cai', 'xin-yi', 'hui-jun']By keys():   ['hui-jun', 'xin-yi', 'zheng-cai']D:\Python27\test>