new_contents:  #!/usr/bin/env python
   import sys
  
   # maps words to their counts
   word2count = {}
  
   # input comes from STDIN (standard input)
   for line in sys.stdin:
       # remove leading and trailing whitespace
       line = line.strip()
       # split the line into words while removing any empty strings
       words = filter(lambda word: word, line.split())
       # increase counters
       for word in words:
           # write the results to STDOUT (standard output);
           # what we output here will be the input for the
           # Reduce step, i.e. the input for reducer.py
           #
           # tab-delimited; the trivial word count is 1
           print '%s\t%s' % (word, 1)
  
subject: Create mapper.py