08 分布式计算MapReduce--词频统计

WordCount程序任务：

程序

WordCount

输入

一个包含大量单词的文本文件

输出

文件中每个单词及其出现次数（频数），

并按照单词字母顺序排序，

每个单词和其频数占一行，单词和频数之间有间隔

1.用你最熟悉的编程环境，编写非分布式的词频统计程序。

import cProfile
import pstats


def process_file(dst):
    try:
        f = open(dst, "r")  # 打开文件
    except IOError as s:
        print(s)
        return None
    try:
        bvffer = f.read()  # 读文件到缓冲区
    except:
        print('Read File Error!')
        return None
    f.close()
    return bvffer


def process_buffer(bvffer):
    if bvffer:
        word_freq = {}
        # 下面添加处理缓冲区bvffer代码，统计每个单词的频率，存放在字典word_freq
        bvffer = bvffer.lower()
        # 去除文本中的中英文标点符号
        for ch in '“‘!;,.?”':
            bvffer = bvffer.replace(ch, " ")
        words = bvffer.strip().split()
        for word in words:
            word_freq[word] = word_freq.get(word, 0) + 1  # 给单词计数
        return word_freq


def output_result(word_freq):
    if word_freq:
        sorted_word_freq = sorted(word_freq.items(), key=lambda v: v[1], reverse=True)
        for item in sorted_word_freq[:]:
            print(item)


def main():
    dst = "C:\\Users\\acer\\Desktop\\sentence.txt"
    bvffer = process_file(dst)
    word_freq = process_buffer(bvffer)
    output_result(word_freq)


if __name__ == "__main__":
    cProfile.run("main()", "result")
    p = pstats.Stats("result")
    p.strip_dirs().sort_stats("call").print_stats(10)
    p.strip_dirs().sort_stats("cumulative").print_stats()
    p.print_callees("process_buffer")

2.用MapReduce实现词频统计

2.1 编写Map函数

编写mapper.py

#!/usr/bin/env python
import sys
for line in sys.stdin:
    line = line.strip()
    words = line.split()
    for word in words:
        print "%s\t%s" % (word, 1)

授予可运行权限

$ chmod +x mapper.py

本地测试mapper.py

2.2 编写Reduce函数

编写reducer.py

#!/usr/bin/env python
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 word == current_word: 
    print "%s\t%s" % (current_word, current_count)

授予可运行权限

$ chmod +x reducer.py

本地测试reducer.py

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