Question

所以我有两个我想要比较的CSV文件并获得类似项目的结果。第一个文件hosts.csv如下所示：

Path    Filename    Size    Signature
C:\     a.txt       14kb    012345
D:\     b.txt       99kb    678910
C:\     c.txt       44kb    111213

第二个文件masterlist.csv如下所示：

Filename    Signature
b.txt       678910
x.txt       111213
b.txt       777777
c.txt       999999

正如您所看到的行不匹配，并且masterlist.csv始终大于hosts.csv文件。我想要搜索的唯一部分是Signature部分。我知道这看起来像是：

hosts[3] == masterlist[1]

我正在寻找一个能给我类似下面的解决方案（基本上是带有新RESULTS列的hosts.csv文件）：

Path    Filename    Size    Signature    RESULTS
C:\     a.txt       14kb    012345       NOT FOUND in masterlist
D:\     b.txt       99kb    678910       FOUND in masterlist (row 1)
C:\     c.txt       44kb    111213       FOUND in masterlist (row 2)

我搜索了这些帖子，发现了类似于here的内容，但我不太明白，因为我还在学习python。

编辑使用Python 2.6

Answer 1

srgerg的答案极其低效，因为它以二次方式运作;这是一个线性时间解决方案，使用Python 2.6兼容语法：

import csv

with open('masterlist.csv', 'rb') as master:
    master_indices = dict((r[1], i) for i, r in enumerate(csv.reader(master)))

with open('hosts.csv', 'rb') as hosts:
    with open('results.csv', 'wb') as results:    
        reader = csv.reader(hosts)
        writer = csv.writer(results)

        writer.writerow(next(reader, []) + ['RESULTS'])

        for row in reader:
            index = master_indices.get(row[3])
            if index is not None:
                message = 'FOUND in master list (row {})'.format(index)
            else:
                message = 'NOT FOUND in master list'
            writer.writerow(row + [message])

这将生成一个字典，首先将masterlist.csv的签名映射到行号。字典中的查找需要恒定时间，使第hosts.csv行的第二个循环与masterlist.csv中的行数无关。更不用说代码更简单了。

对于那些使用Python 3的人，上面只需要调整open()调用以在文本模式下打开（从文件模式中删除b），并且你想添加{{1因此CSV阅读器可以控制行分隔符。您可能希望声明显式使用的编码，而不是依赖于系统默认值（使用new line=''）。可以使用字典理解（encoding=...）构建master_indices映射。

Answer 2

修改：虽然我的解决方案正常运行，但请查看下面的Martijn答案，以获得更有效的解决方案。

您可以找到python CSV模块here的文档。

您正在寻找的是这样的：

import csv

f1 = file('hosts.csv', 'r')
f2 = file('masterlist.csv', 'r')
f3 = file('results.csv', 'w')

c1 = csv.reader(f1)
c2 = csv.reader(f2)
c3 = csv.writer(f3)

masterlist = list(c2)

for hosts_row in c1:
    row = 1
    found = False
    for master_row in masterlist:
        results_row = hosts_row
        if hosts_row[3] == master_row[1]:
            results_row.append('FOUND in master list (row ' + str(row) + ')')
            found = True
            break
        row = row + 1
    if not found:
        results_row.append('NOT FOUND in master list')
    c3.writerow(results_row)

f1.close()
f2.close()
f3.close()

Answer 3

Python的CSV和集合模块，特别是OrderedDict，在这里非常有用。你想使用OrderedDict来保存键的顺序等等。你不必这样做，但它很有用！

import csv
from collections import OrderedDict


signature_row_map = OrderedDict()


with open('hosts.csv') as file_object:
    for line in csv.DictReader(file_object, delimiter='\t'):
        signature_row_map[line['Signature']] = {'line': line, 'found_at': None}


with open('masterlist.csv') as file_object:
    for i, line in enumerate(csv.DictReader(file_object, delimiter='\t'), 1):
        if line['Signature'] in signature_row_map:
            signature_row_map[line['Signature']]['found_at'] = i


with open('newhosts.csv', 'w') as file_object:
    fieldnames = ['Path', 'Filename', 'Size', 'Signature', 'RESULTS']
    writer = csv.DictWriter(file_object, fieldnames, delimiter='\t')
    writer.writer.writerow(fieldnames)
    for signature_info in signature_row_map.itervalues():
        result = '{0} FOUND in masterlist {1}'
        # explicit check for sentinel
        if signature_info['found_at'] is not None:
            result = result.format('', '(row %s)' % signature_info['found_at'])
        else:
            result = result.format('NOT', '')
        payload = signature_info['line']
        payload['RESULTS'] = result

        writer.writerow(payload)

以下是使用测试CSV文件的输出：

Path    Filename        Size    Signature       RESULTS
C:\     a.txt   14kb    012345  NOT FOUND in masterlist 
D:\     b.txt   99kb    678910   FOUND in masterlist (row 1)
C:\     c.txt   44kb    111213   FOUND in masterlist (row 2)

请原谅错位，它们是分开的：）

Answer 4

csv模块在解析csv文件时非常方便。但只是为了好玩，我只是简单地在空格上分割输入来获取数据。

只需解析数据，为masterlist.csv中的数据构建dict，其中签名为key，行号为value。现在，对于hosts.csv的每一行，我们只需查询dict并查明masterlist.csv中是否存在相应的条目，如果存在，则查找该行。

#! /usr/bin/env python

def read_data(filename):
        input_source=open(filename,'r')
        input_source.readline()
        return [line.split() for line in input_source]

if __name__=='__main__':
        hosts=read_data('hosts.csv')
        masterlist=read_data('masterlist.csv')
        master=dict()
        for index,data in enumerate(masterlist):
                master[data[-1]]=index+1
        for row in hosts:
                try:
                        found="FOUND in masterlist (row %s)"%master[row[-1]]
                except KeyError:
                        found="NOT FOUND in masterlist"
                line=row+[found]
                print "%s    %s    %s    %s    %s"%tuple(line)

Answer 5

我只是在Martijn Pieters代码中修复了一个小问题，以使其能够在Python 3中工作，并且在此代码中，我试图将file1 row[0]中的第一列元素与第一列元素进行匹配在文件2 row[0]中。

import csv
with open('file1.csv', 'rt', encoding='utf-8') as master:
    master_indices = dict((r[0], i) for i, r in enumerate(csv.reader(master)))

    with open('file2.csv', 'rt', encoding='utf-8') as hosts:
        with open('result.csv', 'w') as results:    
            reader = csv.reader(hosts)
            writer = csv.writer(results)

            writer.writerow(next(reader, []) + ['RESULTS'])

            for row in reader:
                index = master_indices.get(row[0])
                if index is not None:
                    message = 'FOUND in master list (row {})'.format(index)
                    writer.writerow(row + [message])

                else:
                     message = 'NOT FOUND in master list'
                     writer.writerow(row + [message])

        results.close()

比较两个CSV文件并搜索类似的项目

5 个答案: