理解MapReduce

标签：apr   line   理解   ima   字母   tor   else   try   str   

1. 用Python编写WordCount程序并提交任务

1. 编写map函数，reduce函数

   #！ /usr/bin/python3
   # Map函数
   import sys
   for line in sys.stdin:
        line=line.strip()
        words=line.split()
        for word in words:
             print (‘%s\t%s‘ % (word,1))

   #! /usr/bin/python3
   
   # Reduce函数
   from operator import itemgetter
   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))

    

2. 将其权限作出相应修改

   sudo chmod 777 mapper.py
   sudo chmod 777 reducter.py

    

3. 本机上测试运行代码

   echo "Hello World, Bye World" | ./mapper.py
   
   echo "Hello World, Bye World" | ./mapper.py | sort -k1,1 | ./reducter.py

    

4. 放到HDFS上运行
   1. 将之前爬取的文本文件上传到hdfs上
   2. 用Hadoop Streaming命令提交任务
5. 查看运行结果

理解MapReduce

标签：apr   line   理解   ima   字母   tor   else   try   str   

原文地址：https://www.cnblogs.com/a305810827/p/9021872.html