［MapReducer］求平均数

这是Udacity的课程 intro to hadoop and mapReduce里面Lesson4的练习

只说一点，求平均不能在combiner中进行

算法依然是计数，记录总和，最后输出 平均值

#Mapper
#!/usr/bin/python
import sys
from datetime import datetime
for line in sys.stdin:
data = line.strip().split("t")
if len(data) == 6:
weekday = datetime.strptime(data[0], "%Y-%m-%d").weekday()
sale = data[4]
print "{0}t{1}".format(weekday, sale)
#Reducer
#!/usr/bin/python
import sys
count = 0
oldKey = None
totalSales = 0
for line in sys.stdin:
data_mapped = line.strip().split("t")
if len(data_mapped) != 2:
continue
thisKey, thisValue = data_mapped
if oldKey and oldKey != thisKey:
print oldKey, "t", totalSales / count
oldKey = thisKey
count = 0
totalSales = 0
oldKey = thisKey
count += 1
totalSales += float(thisValue)
if oldKey != None:
print oldKey, "t", totalSales / count

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