sales_reducer.py

#!/usr/bin/env python

import sys

value_count=0
sales_quantity_sum=0
sales_price_sum=0
line_amount_sum=0

last_key=None
	
for line in sys.stdin:

	line=line.strip();
	if(line==''):
		break
	key,value = line.split("\t")
	if(last_key==None):
		last_key=key
	values=value.split(",")
	sales_quantity=int(values[0])
	sales_price=float(values[1])
	line_amount=float(values[2])
	if key == last_key:
		sales_quantity_sum+=sales_quantity
		sales_price_sum+=sales_price
		line_amount_sum+=line_amount
		value_count+=1;
	else:
		sales_price_average=sales_price_sum/value_count
		value=str(sales_quantity_sum)+","+str(sales_price_average)+","+str(line_amount_sum)
		print(last_key+"\t"+value)
		value_count=1
		sales_quantity_sum=sales_quantity
		sales_price_sum=sales_price
		line_amount_sum=line_amount
		last_key = key
		
if value_count>0:
		sales_price_average=sales_price_sum/value_count
		value=str(sales_quantity_sum)+","+str(sales_price_average)+","+str(line_amount_sum)	
		print(last_key+"\t"+value)