MRJob： - 在map reduce中显示中间值

Question

如何在使用python MRJob库运行mapreduce程序时在终端上显示中间值（即打印变量或列表）？

Answer 1

您可以使用sys.stderr.write（）将结果输出为标准错误。这是一个例子：

from mrjob.job import MRJob
import sys
class MRWordCounter(MRJob):
    def mapper(self, key, line):
        sys.stderr.write("MAPPER INPUT: ({0},{1})\n".format(key,line))
        for word in line.split():
            yield word, 1

    def reducer(self, word, occurrences):
        occurencesList= list(occurrences)
        sys.stderr.write("REDUCER INPUT: ({0},{1})\n".format(word,occurencesList))
        yield word, sum(occurencesList)

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