Python上的Topn记录MapReduce

我是MapReduce的新手，我有一个非常简单的问题。我解决了字数问题，然后我想将问题更改为文本上的Top N记录。虽然我对文本上的所有单词进行排序，但我不能取最后的N值。首先，我阅读文本并用1将每个单词发送给reducer，然后reducer为每个不同的单词找到数字单词。然后我试着根据单词的出现情况对这些单词进行排序。但我找不到排名前N的唱片

from mrjob.job import MRJob
from mrjob.step import MRStep
from stemming.porter2 import stem
class MRWordCount(MRJob):
     def steps(self):
            return [
                MRStep(mapper=self.mapper,
                    reducer=self.reducer),
                MRStep(mapper=self.secondmapper,
                    reducer = self.secondreducer)
                ]

    def mapper(self,_,lines): 
       words = lines.strip().split()
       for w in words:
            yield stem(w.lower()),1 

    def reducer(self, key, values): 
       yield key, (sum(values))

    def secondmapper(self, key,value):       
       yield '%04d'%int(value), key 

    def secondreducer(self, key, values):       
       for v in values:           
            yield v,key  

if __name__ == '__main__':
    MRWordCount.run()

---

我用下面的代码解决了这个问题

from mrjob.job import MRJob
from mrjob.step import MRStep
from stemming.porter2 import stem


class MRWordCount(MRJob):
    def steps(self):
            return [
                MRStep(mapper=self.mapper,
                    reducer=self.reducer),
                MRStep(reducer = self.secondreducer)
                ]

    def mapper(self,_,lines):
       words = lines.strip().split()
       for w in words:
            w = unicode(w, "utf-8", errors="ignore")
            yield stem(w.lower()),1 

    def reducer(self, key, values): 
       yield None, ('%04d'%int(sum(values)),key)

    def secondreducer(self, key, values):   
       self.aList= []    
       for v in values:
            self.aList.append(v)
       count = len(self.aList)
       for m in range(count-5,count):
          yield self.aList[m]


if __name__ == '__main__':
    MRWordCount.run()