程式碼如下：

#encoding=utf-8

print '中國'

#給字典型別增加排名功能
from bisect import bisect_left, insort_left
import UserDict
class Ratings(UserDict.DictMixin, dict):   
    def __init__(self, *args, **kwds):    
        dict.__init__(self, *args, **kwds)
        # self._rating is the crucial auxiliary data structure: a list
        # of all (value, key) pairs, kept in "natural"ly-sorted order
        self._rating = [ (v, k) for k, v in dict.iteritems(self) ]
        self._rating.sort( )
    def copy(self):       
        return Ratings(self)
    def __setitem__(self, k, v):      
        if k in self:
            del self._rating[self.rating(k)]
        dict.__setitem__(self, k, v)
        insort_left(self._rating, (v, k))
    def __delitem__(self, k):     
        del self._rating[self.rating(k)]
        dict.__delitem__(self, k)

    __len__ = dict.__len__
    __contains__ = dict.__contains__
    has_key = __contains__
    
    def __iter__(self):
        for v, k in self._rating:
            yield k
    iterkeys = __iter__
    def keys(self):
        return list(self)
    
    def rating(self, key):
        item = self[key], key
        i = bisect_left(self._rating, item)
        if item == self._rating[i]:
            return i
        raise LookupError, "item not found in rating"
    def getValueByRating(self, rating):
        return self._rating[rating][0]
    def getKeyByRating(self, rating):
        return self._rating[rating][1]


r = Ratings({"1": 2, "12": 123})
print [r.rating(key) for key in ["12", "12", "1"]]
 

列印結果如下：

中國
[1, 1, 0]