CODEWITHSUNDEEP
pythonregexregex-group
buhtz
buhtz

Reputation: 12202

Second optional capturing group depending on optional delimiter in regex

I'm sorry for asking this maybe duplicate question. I checked the existing questions and answers about optional capturing groups. I tried some things but I'm not able to translate the answer to my own example.

This are two imput lines

id:target][label
id:target

I would like to capture id: (group 1), target (group 2) and if ][ is present label (group 3).

The used regex (Python regex) only works on the first line (live example on regex101).

^(.+:)(.*)\]\[(.*)

enter image description here

In the other examples I don't get what the regex makes a capturing group optional. And maybe the delimiter ][ used by me also mix up with my understanding problem.

One thing I tried was this

^(.+:)(.*)(\]\[(.*))?

This doesn't work as expected enter image description here

Upvotes: 0

Views: 65

Answers (1)

The fourth bird
The fourth bird

Reputation: 163447

You could write the pattern using an anchor at the end, a negated character class for group 1, a non greedy quantifier for group 2 and then optionally match a 3rd part:

^([^:]+:)(.*?)(?:]\[(.*))?$

Explanation

  • ^ Start of string
  • ([^:]+:) Group 1, match 1+ chars other than : and then match : using a negated character class
  • (.*?) Group 2, match any char, as few as possible
  • (?: Non capture group to match as a whole part
    • ]\[ Match ][
    • (.*) Group 3, match any character
  • )? Close the non capture group and make it optional
  • $ End of string

See a regex101 demo

If you are only matching for example word characters, this you might consider:

^([^:]+:)(\w+)(?:]\[(\w+))?

See a another regex101 demo

Upvotes: 1

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