hadoop_sorted/mr/python/reducer.py

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2024-04-05 17:14:07 +02:00
#!/usr/bin/env python
from operator import itemgetter
import sys
current_word = None
current_count = 0
word = None
results = []
# input comes from STDIN
for line in sys.stdin:
# remove leading and trailing whitespace
line = line.strip()
# parse the input we got from mapper.py
word, count = line.split('\t', 1)
# convert count (currently a string) to int
try:
count = int(count)
except ValueError:
# count was not a number, so silently
# ignore/discard this line
continue
# this IF-switch only works because Hadoop sorts map output
# by key (here: word) before it is passed to the reducer
if current_word == word:
current_count += count
else:
if current_word:
# write result to STDOUT
#print('%s\t%s' % (current_word, current_count))
results.append((current_word, len(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))
results.append((current_word, len(current_word), current_count))
results.sort(key=lambda x: x[1])
for result in results:
print('%s\t%s' % (result[0], result[2]))