CODEWITHSUNDEEP
regex
Richard Guy
Richard Guy

Reputation: 80

Optionally match part of a regular expression?

I have the following regular expression:

(?P<a>\d+)\s(?P<b>.+)\s\((?P<c>.+)\)\s(?P<d>\d+)

The strings I'm trying to match are: "1 Something (code) 123" Should match as a=1, b=Something, c=code, d=123

"1 Something" Should match as a=1, b=Something (no match for c or d)

My expression doesn't match the second string. How can I make the "(code) 123" part optional?

Upvotes: 0

Views: 68

Answers (1)

The fourth bird
The fourth bird

Reputation: 163287

You can use a nested group, and make the part for group d optional. As Something is a single word, you can use \S+ instead of .+

(?P<a>\d+)\s(?P<b>\S+)(?:\s\((?P<c>[^()\n]+)\)(?:\s(?P<d>\d+))?)?

The pattern matches:

  • (?P<a>\d+)\s(?P<b>\S+) Match group a, a whitespace char and group b, where group 2 matches 1+ non whitespace chars instead of .+
  • (?: Non capture group
    • \s\((?P<c>[^()\n]+)\) Match a whitspace char and group c
    • (?:\s(?P<d>\d+))? Optionally match group d
  • )? Close the non capture group and make it optional

Regex demo

Upvotes: 1

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