删除最外面的括号

Question

I am having problem while removing outermost parentheses from a string using GREL. What i am trying to do is simply remove outermost parentheses and all other parentheses should be kept intact. Below is what i am trying to do using regex -

value.split(/(abc+/)

and below is my sample string that i am trying to parse and desired output.

Foo ( test1 test2 ) => Foo test1 test2
Bar ( test1 t3() test2 ) => Bar test1 t3() test2
Baz ((("Fdsfds"))) => Baz (("Fdsfds"))

I would appreciate any help.

Answer 1

One option could be to use a capturing group and in the replacement use the first capturing group.

Note that this does not take balanced parenthesis into account.

It matches the outer parenthesis, then captures in a group what is inside and matches an outer parenthesis again.

Inside the capturing group is an alternation that matches not () or from an openening till closing parenthesis.

\((\(*(?:[^)(]*|\([^)]*\))*\)*)\)

Explanation

• \\( Match outer parenthesis (
• ( Capture group - \\(* Match 0+ times (
  • (?: Non capturing group
    • [^)(]* Match 0+ times not ( or )
    • | Or
    • \\([^)]*\\) Match from ( till next ) closing parenthesis
  • )* Close non capturing group and repeat 0+ times
  • \\)* Match 0+ times a closing parenthesis
• ) Close capture group
• \\) Match outer closing parenthesis

Regex demo

Answer 2

I am not familiar at all with grel or openrefine regex syntax or limitation, in a broader context you can use one of the following regexes depending on what regex engine is used.

PCRE regex:

^[^(]*\K\(|\)(?!.*\).*)

demo: https://regex101.com/r/lj0Qbl/1/

ECMA regex:

(?<!.*\(.*)\(|\)(?!.*\).*)

demo: https://regex101.com/r/g8XbjI/1/

for both:

Input:

Foo ( test1 test2 ) bob
Bar ( test1 t3() test2 ) bob
Baz ((("Fdsfds"))) bob

Output:

Foo  test1 test2  bob
Bar  test1 t3() test2  bob
Baz (("Fdsfds")) bob

Answer 3

If our inputs are all similar to those listed in the question, this expression might work:

(.+?)\s+\((\s+)?(.*)(\s+)?\)

and we would replace it with $1 $3 .

Demo

RegEx Circuit

jex.im visualizes regular expressions:

Answer 4

There are multiple ways of doing this with GREL. If you want to use regular expressions then in GREL I'd recommend combining this with the GREL match function:

value.match(/(.*?)\((.*)\)(.*)/).join("")

Note that this expression assumes there is at least one pair of parentheses in the cell - cells that have no parentheses or have only an opening or only a closing parentheses will give an error - however you can use the option 'on error keep original' (which is the default) when doing a cell transformation to keep the original value in these cases