目的：通过python模拟mr，计算每年的最高气温。

1. 查看数据文件，需要截取年份和气温，生成key-value对。

[tianyc@TeletekHbase python]$ cat test.dat

0067011990999991950051507004...9999999N9+00001+99999999999...

0043011990999991950051512004...9999999N9+00221+99999999999...

0043011990999991950051518004...9999999N9-00111+99999999999...

0043012650999991949032412004...0500001N9+01111+99999999999...

0043012650999991949032418004...0500001N9+00781+99999999999...

2. 编写map，打印key-value对

[tianyc@TeletekHbase python]$ cat map.py

import re

import sys

for line in sys.stdin:

  val=line.strip()

  (year,temp)=(val[15:19],val[40:45])

  print "%s\t%s" % (year,temp)

[tianyc@TeletekHbase python]$ cat test.dat|python map.py

1950 +0000

1950 +0022

1950 -0011

1949 +0111

1949 +0078

3. 将结果排序

[tianyc@TeletekHbase python]$ cat test.dat|python map.py |sort

1949 +0078

1949 +0111

1950 +0000

1950 -0011

1950 +0022

4. 编写redurce，对map中间结果进行处理，生成最终结果

[tianyc@TeletekHbase python]$ cat red.py

import sys

(last_key,max_val)=(None,0)

for line in sys.stdin:

  (key,val)=line.strip().split('\t')

  if last_key and last_key!=key:

    print '%s\t%s' % (last_key, max_val)

    (last_key, max_val)=(key,int(val))

else:

  (last_key, max_val)=(key,max(max_val,int(val)))

if last_key:

  print '%s\t%s' % (last_key, max_val)

5. 执行。

[tianyc@TeletekHbase python]$ cat test.dat|python map.py |sort|python red.py

1949 111

1950 22

后继测试参见