Python regexp replace text inside tags

Question

I'm trying replace a block of text inside of tags with python sub.

Block of text:

text = """##startBlablaTag##
          blablabla
          blebleble
          bliblibli
          ##endtBlablaTag##

Using the following regexp with "search" I can catch what's inside of the tags

>>> re.search(r'^##\w+Blabla\w+##\n(.*)##\w+Blabla\w+##', text, re.MULTILINE | re.DOTALL).group(1)
'blablabla\blebleble\bliblibli\n'
>>>

but when I try with "sub" to replace, I can't replace the whole content, just the end...

>>> re.sub(r'^##\w+Blabla\w+##\n(.*)##\w+Blabla\w+##', r'\g<1>test!', text, flags=re.MULTILINE | re.DOTALL)
'blablabla\nblebleble\nbliblibli\ntest!'

Expected:

##startBlablaTag##
test!
##endtBlablaTag##

Anybody knows how to replace the whole content inside the tags?

Thanks!

@Aran-Fey sorry, post edited.

chrigu
– chrigu

2018-03-27 21:29:51 +00:00
Commented Mar 27, 2018 at 21:29 — chrigu
– chrigu, Commented Mar 27, 2018 at 21:29

Aran-Fey · Accepted Answer · 2018-03-27 21:42:01Z

1

You're doing it backwards.

The regex you used is this:

^##\w+Blabla\w+##\n(.*)##\w+Blabla\w+##

As you can see, you have used a capture group to capture the text inside of the tag. In other words, you've captured the text that you want to remove. This serves no purpose - you should be using capture groups around the text that you want to keep. In other words, the regex should look like this:

^(##\w+Blabla\w+##\n).*(##\w+Blabla\w+##)

Now you can use backreferences to refer to the captured text during the substitution and insert new text inside of the tags:

>>> re.sub(r'^(##\w+Blabla\w+##\n).*(##\w+Blabla\w+##)', r'\1test!\2', text, flags=re.S)
'##startBlablaTag##\ntest!##endtBlablaTag##'

answered Mar 27, 2018 at 21:42

Aran-Fey

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