How do I match a nested bracket and brace pair while ignoring single instances using regex?

Asked Apr 26 '18 at 15:32

Active Apr 26 '18 at 15:32

Viewed 26 times

Given lines such as:

[{ ERR }]
 { ABC }
 [ NT1 ]

 [ XYZ }  <- This is an illegal form and should also be ignored

How do I write a regex that will capture the first segment, but ignore the others if I read line by line. So if there is one nested pair of [] and one pair of {} it will match that, and then not match on the other lines.

I've attempted to do this using the expression ([ \[]*([ \{]*[a-zA-Z]+[ \} ]*)[ \] ]*)

I'm also trying to output the three alphanumerics in the center as a match subgroup (there will never be more than three char). Whitespace is irrelevant.

asked Apr 26 '18 at 15:32

Integration

1

How nested can they be? `[{[{XYZ}]}]` possible? What about `[{ABC}{XYZ}]`? Also, are you trying to match `{ABC}` or just the contents `ABC`? Are you performing a replace? – ctwheels Apr 26 '18 at 15:33
@ctwheels [{ ABC }] is what I am looking for. They will be more nested in larger groups of already nested segments, but that's something I'd like to tackle on my own once I get a better grasp of the regex. Thanks – Integration Apr 26 '18 at 15:35
1

I think you want `\[\{.*\}\]`? – Aran-Fey Apr 26 '18 at 15:36
As it stands, `\[{[^}]*}]` works for your given samples – ctwheels Apr 26 '18 at 15:38
@Aran-Fey That was quick. Thanks - regex is not my strong point. – Integration Apr 26 '18 at 15:38
@Aran-Fey that can give unexpected results. Test against `[{ABC}] some random text here [{XYZ}]` – ctwheels Apr 26 '18 at 15:42
I've modified @Aran-Fey answer to output the center alphanumerics as a subgroup : `\[\{(.*)\}\]` – Integration Apr 26 '18 at 15:48
Use `r'\[\{(.*?)}]'` – Wiktor Stribiżew Apr 26 '18 at 16:45

How do I match a nested bracket and brace pair while ignoring single instances using regex?

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