How to write the regex in Python to maintain the group content unchanged?

Question

I'm trying to use python to run regex to do the replacement like below:

a = "%I'm a sentence.|"
re.sub(r"%(.*?)\|", "<\1>", a)

Then b = <\1>, but I want to get the result of <I'm a sentences.>

How am I supposed to achieve this? I tried to group I'm a sentence, but I feel I did something wrong, so the result doesn't maintain the group 1. If you have any ideas, please let me know. Thank you very much in advance!

As always with regex, use raw string literals: `r"<\1>"` – Aran-Fey Aug 09 '17 at 08:27 — Aran-Fey, Aug 09 '17 at 08:27

score 5 · Accepted Answer · answered Aug 09 '17 at 08:27

5

Use a raw string for the replacement, otherwise \1 will be interpreted as an octal character code, not a back-reference.

And assign the result to b.

b = re.sub(r"%(.*?)\|", r"<\1>", a)

DEMO

answered Aug 09 '17 at 08:27

Barmar

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Thanks, @barmar! This helped a lot! – Penny Aug 09 '17 at 08:57

score 3 · Answer 2 · answered Aug 09 '17 at 08:28

3

to capture group use \g<1>

a = "%I'm a sentence.|"
a = re.sub(r"%(.*?)\|", "<\g<1>>", a)
# <I'm a sentence.>

answered Aug 09 '17 at 08:28

ewwink

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How to write the regex in Python to maintain the group content unchanged?

2 Answers2