正则表达式替换 python 中字符串内的 substring

Question

I have to replace a substring with another string in a file.

Below is the line which is present in the file.

Input: #pragma MESSAGE "Hello World" 0000=1 /* Clarification 0001: [[Specific Clarification]] */

Expected Output: #pragma MESSAGE "Hello World" 0000=1 # [[Specific Clarification]]

Below is my code:

import re
line = r'#pragma MESSAGE "Hello World" 0000=1 /* Clarification 0001: [[Specific Clarification]] */'
comment = re.search(r'([\/\*]+).*([^\*\/]+)', line)
replace = re.search(r'([\[[]).*([\]]])', comment.group())
replaceWith = replace.group()
content_new = re.sub(r'([\/\*]).*([\*\/])', '# ' + replaceWith, line)

Is there an optimal solution for the above code?

Answer 1

You need to match comments, say, with Regex to match a C-style multiline comment , and then replace the [[...]] substring inside the matches. This approach is safest, it won't fail if there is [[ and no ]] inside the comment, and there are several such comments in the string.

The sample code snippet will look like

import re
line = r'#pragma MESSAGE "Hello World" 0000=1 /* Clarification 0001: [[Specific Clarification]] */'
content_new = re.sub(r'/\*[^*]*\*+(?:[^/*][^*]*\*+)*/', lambda x: re.sub(r'.*(\[\[.*?]]).*', r'# \1', x.group()), line)
print(content_new)

Output: #pragma MESSAGE "Hello World" 0000=1 # [[Specific Clarification]] .

Details:

• re.sub(r'/\*[^*]*\*+(?:[^/*][^*]*\*+)*/', ..., line) - finds all C style comments in the string, and
• lambda x: re.sub(r'.*(\[\[.*?]]).*', r'# \1', x.group()) is the replacement: x is the match data object with the comment text, it matches any text up to [[ , then captures [[ and then any text up to and including ]] , and then matches the rest of the comment, and replaces with # , space and the Group 1 value. See the regex demo here .