How to replace spaces in "§ 1", "§s 1, 2, [indeterminate number]" all with underscores in regex?

I have a simple regex pattern that replaces a space between paragraph sign and a number with an underscore: Find: § (\d+) Replace: §_$1

It works fine and turns "§ 5" into "§_5", but here are cases when there are more numbers following the paragraphs sign, so how to turn "§s 23, 12" also into "§s_1,_2_and_3"? Is it possible with regex?

I have tried modifying the original regex pattern, (§|§-d) (\d+) finds only some of the cases, and I have no idea how to write the replacement.

Thanks in advance!

Solution

You can use

re.sub(r'§\w*\s+\d+(?:,\s*\d+)*', lambda x: re.sub(r'\s+', '_', x.group()), text)

The re.sub(r'\s+', '_', x.group() replaces chunks of one or more whitespaces with a single _ char.

See the regex demo, details:

§ - a § char
\w* - zero or more word chars
\s+ - one or more whitespaces
\d+ - one or more digits
(?:,\s*\d+)* - zero or more sequences of a comma, zero or more whitespaces and one or more digits.

See the Python demo:

import re
text = "§s 23, 12"
print(re.sub(r'§\w*\s+\d+(?:,\s*\d+)*', lambda x: re.sub(r'\s+', '_', x.group()), text))
# => §s_23,_12