一：先寫map類

import sys
for line in sys.stdin:
line = line.strip( )
words = line.split( )
for word in words:
print(‘%s\t%s‘ % (word, 1))

二：寫reduce類

import sys
current_word = None
current_count = 0
word = None
for line in sys.stdin:
line = line.strip()
word, count = line.split(‘\t‘,1)
try:
count = int(count)
except ValueError:
continue
if current_word == word:
current_count += count
else:
if current_word:
print(‘%s\t%s‘ % (current_word,current_count))
current_count = count
current_word = word
if current_word == word:
print(‘%s\t%s‘ % (current_word,current_count))

三：利用hadoop Streaming執行Python的內容。

hadoop jar /home/hadoop/hadoop-2.6.0-cdh5.5.2/share/hadoop/tools/lib/hadoop-streaming-2.6.0-cdh5.5.2.jar -input /user/hadoop/aa.txt -output /user/hadoop/python_output -mapper "python mapper.py" -reducer "python reducer.py" -file mapper.py -file reducer.py

說明：

輸入和輸出路徑，本身就是hdfs上的，不需要特殊指定hdfs。

不加黃色部分的引號的話，會報錯誤：

Error: java.lang.RuntimeException: PipeMapRed.waitOutputThreads(): subprocess failed with code 2

不加粉色部分的內容的話，會報錯誤：

Error: java.lang.RuntimeException: Error in configuring object

本文出自 “白話” 博客，請務必保留此出處http://feature09.blog.51cto.com/12614993/1970964

Streaming執行Python版WordCount