CODEWITHSUNDEEP
python-3.xregexregex-lookarounds
ta8
ta8

Reputation: 323

Regex - do not match any inner brackets if outer brackets are preceded by specific character

I am trying to come up with a regular expression that solves the following problem: Of the below string, I only want to match (e):

$(a(b)(c)d)(e)

Of the below string, I only want to match (e(f)):

$(a(b)(c)d)(e(f))

The expression I came up with will only exclude the first inner bracket:

(?<!\$[^)]*)\(.+?\)

Here's the interactive example: regexr.com/5n5c1

I use regular expressions in Python 3 with the regex library.

Upvotes: 1

Views: 132

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626950

Install PyPi regex module (pip install regex) and then you will be able to use

import regex
strs = ['$(a(b)(c)d)(e)', '$(a(b)(c)d)(e(f))']
rx = r'\$(\((?:[^()]++|(?1))*\))(*SKIP)(*F)|(\((?:[^()]++|(?2))*\))'
for s in strs:
  print( [x.group() for x in regex.finditer(rx, s)] )

See the Python demo.

Details

  • \$(\((?:[^()]++|(?1))*\))(*SKIP)(*F) - a $ char and then a substring between the balanced nested round brackets, and then the (*SKIP)(*F) verbs make the current match fail and skip it, starting the next pattern search from the place where the skip occurred
  • | - or
  • (\((?:[^()]++|(?2))*\)) - a substring between the balanced nested round parentheses.

See the regex demo.

Upvotes: 1

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