from mrjob.job import MRJob
from mrjob.step import MRStep
import re

WORD_RE = re.compile(r"[\w']+")

class MRWordFrequencyCount(MRJob):

    def mapper(self, _, line):
        for word in WORD_RE.findall(line):
            yield word, 1
    def steps(self):
        return [
            MRStep(mapper=self.mapper,
                   reducer=self.reducer_count_words),
            MRStep(reducer=self.reducer_find_max_word)
        ]

    def reducer_count_words(self, key, values):
        yield None, (sum(values), key)
    def reducer_find_max_word(self, _, kvp):
        yield max(kvp)

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