Feature or enhancement

Every match, search, or fullmatch on a pattern with no capturing groups allocates capture-group bookkeeping, then frees it without ever reading it. Group-less patterns are common in validation and scanning code, so this runs often.

Examples:

• Checking the format of millions of records during an import, e.g. re.match(r"\d{4}-\d{2}-\d{2}", value).
• Scanning each log line with re.search(r"ERROR|WARN", line).
• Routers and frameworks testing many small patterns per request.

Proposed change: skip that allocation when a pattern has no capturing groups. Patterns with groups stay untouched, and results are identical.

On a local optimized build, re.match and re.search run 11 to 13 percent faster for group-less patterns on short inputs, with no change for patterns that use groups.

Linked PRs

• gh-150717: Avoid mark-array allocation for groupless regex patterns #150719