Python - Mrjob inlink count / MapReduce

Question

I would like to count the number of times that a word appears in a line of my doc with MrJob and Mapreduce.

I just succeed to count the number of time a song appear in my doc but I don't know how to count word inlink.

    %%file wordcountX.py

from mrjob.job import MRJob # import the mrjob library

class WordCount(MRJob):
  #create a mapper()
  def mapper(self, _, line):
    for word in line.strip().split(' '):
      if len(word) > 0:
       yield (word, 1)

  #create a reducer()
  def reducer(self, word, count):
    yield (word, sum(count))

if __name__ == "__main__":
    WordCount.run()

! python wordcountX.py songplays.txt

Do you know how to do that ?