Regex grouping
A regex capturing group is a parenthesized regular-expression subpattern whose matched text is retained for separate access or reference.
The Well-Grounded Rubyist, Fourth Edition
A submatch is the substring matched by a parenthesized subpattern within a regular-expression match.
- How it is used
- Isolates useful substrings within regular-expression matches for field extraction and string substitution.
- How deep it goes
- Works through numbering, nested and named groups, optional captures, non-capturing groups, and retrieval through MatchData.
- Examples
- Uses comma-separated personal fields, a phone number, nested groups, scanned names, and a corrected letter transposition.
- What you can do after
- Applies it via Ruby’s match, scan, sub, and gsub to extract fields and reuse captures in replacements.
Read how The Well-Grounded Rubyist, Fourth Edition explains regex grouping →
Secrets of the JavaScript Ninja, Second Edition
A regular-expression subgroup whose matched text is recorded for later access or reference.
- How it is used
- Extracts matched substrings for later access, backreferences, and replacement logic.
- How deep it goes
- Works through capture positions and the different results of local match, global match, and repeated exec calls.
- Examples
- Uses CSS translateY extraction, HTML-tag matches, and dashed-string camel casing.
- What you can do after
- Apply captures via String.match, RegExp.exec, or String.replace to extract or transform matched text.
Read how Secrets of the JavaScript Ninja, Second Edition explains regex grouping →
Tiny Python Projects: Learn coding and testing with puzzles and games
A capture group is a parenthesized subpattern in a regular expression whose matched text is retained for later retrieval.
- How it is used
- Uses parentheses to retain matched substrings for word transformation, text splitting, and later retrieval.
- How deep it goes
- Explains group retrieval, numbering, optionality, nesting, and non-capturing syntax through runnable examples.
- Examples
- Demonstrates consonant-vowel word parsing, capitalization-preserving transformations, captured separators, and optional nested patterns.
- What you can do after
- Apply it via Python's re module to extract, reuse, or preserve selected portions of matched text.
The Quick Python Book, Fourth Edition
A capturing group is a parenthesized regular-expression subpattern whose matched text is retained for later retrieval.
- How it is used
- Groups alternatives and optional fields, then retains named fields for extraction from matched name-and-phone records.
- How deep it goes
- Works through grouping, optionality, named capture, and retrieval with `group()`; leaves broader regex subtleties to `re` documentation.
- Examples
- Uses `(h|H)ello`, optional phone area codes, and a name-and-phone record parser with named fields.
- What you can do after
- Apply it via Python `re` to match optional fields and retrieve named values from a successful search.
Read how The Quick Python Book, Fourth Edition explains regex grouping →
Modern C, Third Edition
A capture is a lambda specification identifying variables from the surrounding scope that are made available inside the lambda.
- How it is used
- Uses lambda captures to make surrounding expressions available inside a lambda used to implement macros.
- How deep it goes
- Defines init-capture syntax and its inferred, const-qualified semantics, but leaves writable captures beyond scope.
- Examples
- Uses pointer init-captures in a `SWAP` macro to bring its operands into a lambda.
- What you can do after
- Understand how init-captures make surrounding expressions available inside a lambda.
Python How-To
A capturing group is a delimited subexpression in a regular expression whose matched substring is retained for later access.
- How it is used
- Extracts individual fields from matched text for further processing.
- How deep it goes
- Explains parentheses, group numbering, and retrieval; flags numbering risks but does not detail named-group mechanics.
- Examples
- Uses a comma-separated phrase and task records with ID, title, and description fields.
- What you can do after
- Apply Python regular-expression matching to extract separate fields from text.
Related concepts
- noncapturing groupcontrasts with · A noncapturing group is a parenthesized regular-expression subpattern that groups matching behavior without storing its matched text as a capture.
- regular expressionpart of · A formal pattern notation that describes sets of strings and enables text to be matched, searched, extracted, or transformed.
- backreferenceused by · A backreference is regular-expression or replacement-string notation that refers to text captured by a capturing group.
- conditional matchused by · A conditional match selects between regular-expression subexpressions according to whether a specified capture was found.
- exec methodproduced by · The JavaScript RegExp exec method searches a string for a match and returns a match result with captures or null if no match is found.
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