Python re.sub text manipulation on matched contents before substituting

[xilex]

Hi, I have the following code below:

import re

t = '<img data src="some-thing">'
pattern = '(<img ).*?(src=")(.*?)(">)'
u = re.sub(pattern, '\\1\\2\\3\\4', t)
print(u)

The output is <img src="some-thing">. Is there a way to do some text manipulation on group 3 so it ends up being <img src="something">? I can't think of a better approach right now. This is a just a basic example of what I am trying to do, the content I am replacing is more complex that just replacing a dash. Thanks.

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Found solution with a function: https://docs.python.org/3/library/re.html#text-munging