Grep 和 Python

问题描述

我需要一种通过 Unix 命令行中的正则表达式使用 grep 搜索文件的方法.例如，当我在命令行中输入:

I need a way of searching a file using grep via a regular expression from the Unix command line. For example when I type in the command line:

python pythonfile.py 'RE' 'file-to-be-searched'

我需要在文件中搜索正则表达式 'RE' 并打印出匹配的行.

I need the regular expression 'RE' to be searched in the file and print out the matching lines.

这是我的代码:

import re
import sys

search_term = sys.argv[1]
f = sys.argv[2]

for line in open(f, 'r'):
    if re.search(search_term, line):
        print line,
        if line == None:
            print 'no matches found'

但是当我输入一个不存在的单词时，找不到匹配项不会打印

But when I enter a word which isn't present, no matches found doesn't print

推荐答案

自然的问题是为什么不直接使用 grep?！但假设你不能......

The natural question is why not just use grep?! But assuming you can't...

import re
import sys

file = open(sys.argv[2], "r")

for line in file:
     if re.search(sys.argv[1], line):
         print line,

注意事项:

• search 而不是 match 来查找字符串中的任意位置
• 逗号 (,) 后 print 删除回车(行将有一个)
• argv 包含python文件名，所以变量需要从1开始

• search instead of match to find anywhere in string
• comma (,) after print removes carriage return (line will have one)
• argv includes python file name, so variables need to start at 1

这不处理多个参数(像 grep 那样)或扩展通配符(像 Unix shell 那样).如果你想要这个功能，你可以使用以下方法获得它:

This doesn't handle multiple arguments (like grep does) or expand wildcards (like the Unix shell would). If you wanted this functionality you could get it using the following:

import re
import sys
import glob

for arg in sys.argv[2:]:
    for file in glob.iglob(arg):
        for line in open(file, 'r'):
            if re.search(sys.argv[1], line):
                print line,

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