替换文件中的所有正则表达式匹配项

Question

Consider a basic regex like a(.+?)a . How can one replace all occurences of that regex in a file with the content of the first group?

Answer 1

Use can use the re module to use regular expressions in python and the fileinput module to simply replace text in files in-place

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Example:

import fileinput
import re

fn = "test.txt" # your filename

r = re.compile('a(.+?)a')
for line in fileinput.input(fn, inplace=True):
  match = r.match(line)
  print match.group() if match else line.replace('\n', '')

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Before:

hello this
aShouldBeAMatch!!!!! and this should be gone
you know

After:

hello this
aShouldBeAMa
you know

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Note: this works because the argument inplace=True causes input file to be moved to a backup file and standard output is directed to the input file , as documented under Optional in-place filtering .

Answer 2

You can use Notepad++ with Version >= 6.0. Since then it does support PCRE Regex.

You can then use your regex a(.+?)a and replace with $1

Answer 3

sed

Are you limited to using Python tools? Because sed works very well.

$ sed -i <filename> "s/a(.+?)a/\1/g"

Vim

In a Vim window, give the following search-and-replace ex command:

:%s/\va(.+?)a/\1/g

Note that many regex characters are escaped in Vim- \v sets "very magic" mode, which removes the need for escaping. The same command with "magic" (the default) is :%s/a\(.\+\?)a/\1/g

Python

If you're looking to do this in Python, BigYellowCactus' answer is excellent (use the re module for regex, and fileinput to modify the file).