reducer.py

#!/usr/bin/env python

import sys

last_id = None
last_value = 0
for line in sys.stdin:
    (date, code, value) = line.split("\t")
    if (date, code) == last_id:
        last_value += value
    else:
        if last_id:
            print("{0},{1},{2}".format(last_id[0], last_id[1], last_value)
        last_id = (date, code)
        last_value = value

if (date, code) == last_id:
    print("{0},{1},{2}".format(last_id[0], last_id[1], last_value)