How to write Reducer code for Hadoop

Question

Hi Team. 

I have written the mapper code for Hadoop with python language. Now I want to write a reducer code. How can I write that?

Answer 1

Hi@akhtar,

You can create a reducer code for Hadoop in python language. You can see the below example. It will give you some ideas.

#!/usr/bin/python
from operator import itemgetter 
import sys 
current_word = ""
current_count = 0 
word = "" 
# Input takes from standard input for myline in sys.stdin: 
   # Remove whitespace either side 
   myline = myline.strip() 
   # Split the input we got from mapper.py word, 
   count = myline.split('\t', 1) 
   # Convert count variable to integer 
   try: 
      count = int(count) 
   except ValueError: 
      # Count was not a number, so silently ignore this line continue
   if current_word == word: 
   current_count += count 
   else: 
      if current_word: 
         # Write result to standard output print '%s\t%s' % (current_word, current_count) 
      current_count = count
      current_word = word
# Do not forget to output the last word if needed! 
if current_word == word: 
   print '%s\t%s' % (current_word, current_count)