Map and Reduce functions to find maximum temperature in Python

Sample dataset which has year and temperature.
200935
200942
200912
201040
201020
201015

Map function in Python:

#!/usr/bin/env python
import re
import sys

for line in sys.stdin:
        val = line.strip()
        (key,value) = (val[0:4],val[4:6])
        print "%s\t%s" % (key,value)

Reduce function in Python:

#!/usr/bin/env python

import sys

(prev_year, max_temp) = (None, -sys.maxint)
for line in sys.stdin:
        (year,temp) = line.strip().split("\t")
        if not prev_year:
                prev_year = year
                max_temp = temp
        if prev_year != year:
                print "%s\t%s" % (prev_year,max_temp)
                prev_year = year
                max_temp = temp
        if prev_year == year:
                max_temp = max(int(max_temp),int(temp))

print "%s\t%s" % (prev_year,max_temp)