real-regex
A drop-in replacement for Python's re, backed by a linear-time, ReDoS-safe C++20 engine — with
bounded lookarounds that the other linear-time engines (RE2, Rust) don't have.
pip install real-regex
Drop-in for re
Import it as re and use the API you already know — compile, search, match, fullmatch, findall,
finditer, sub, subn, split, and Match.group / groups / groupdict / span / start / end:
import real as re
m = re.match(r"(\w+)@(\w+)\.(\w+)", "user@example.com")
m.group(1), m.group(2), m.group(3) # ('user', 'example', 'com')
re.findall(r"\d+", "a1 b22 c333") # ['1', '22', '333']
re.sub(r"\s+", "_", "a b c") # 'a_b_c'
Flags work the same: re.I, re.M, re.S, re.X, re.A. Unicode \w \d \s \b and IGNORECASE
case-folding follow re in text mode.
Why replace re
- No ReDoS.
re(like every backtracking engine) blows up on patterns like(a+)+bagainst a hostile input — seconds, then minutes. real-regex is a Thompson NFA simulation: linear time, always, no catastrophic backtracking, ever. - Bounded lookarounds, still linear.
(?=…)(?!…)(?<=…)(?<!…)— including variable-width lookbehind — match without backtracking. RE2 and Rust drop lookarounds to stay safe; real-regex keeps them. - Faster than
reon most work — the measured multiples (geometric mean, per-case wins and the two accepted losses) live indocs/BENCHMARKS.md§B. Sparse scans, multiline anchors and capture-dense extraction lead; a couple of high-volumesplit/tiny-anchored cases stay slower (CPython's C engine wins there). It is not the fastest engine at raw throughput — it is the safe one that is also quick.
Not re, on purpose
Strict by default — every accepted pattern is guaranteed linear. The unsupported constructs
(backreferences, conditionals, non-binary Unicode properties like \p{Bidi_Class=L}) raise real.error
rather than silently falling back to a backtracking engine, so a compiled pattern is a ReDoS-safety
guarantee, not a maybe. (\p{L} / \p{sc=Greek} / \p{scx=Grek} / \p{Alphabetic} — General_Category,
Script, Script_Extensions and the standard binary properties — are supported, a superset of stdlib
re.) Opt
into delegating those to the standard library re per call with real.compile(pat, fallback=True) (or
module-wide with real.fallback = True) — it may accept them, at the cost of the linear-time guarantee for
that pattern; Pattern.engine ("real" or "re") always tells you which backend you got. A few semantics
differ deliberately (e.g. a nullable loop's final empty capture). Full list:
Differences from Python re.
The wheel also ships the header-only C++ library — real.get_include() returns its path, so the same engine
is available to C++ via #include <real/real.hpp>. Source, benchmarks and the C++ API:
https://github.com/RECHE23/real-regex.
1 maintainer
Release files for real-regex 2026.9.4
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | |
|---|---|---|---|
| real_regex-2026.9.4.tar.gz | 679.1 kB | Details |
Built distributions (wheels)
| File | Reset | |||
|---|---|---|---|---|
| real_regex-2026.9.4-cp311-abi3-win_amd64.whl | CPython 3.11 | abi3 | Windows x86-64 | Details |
| real_regex-2026.9.4-cp311-abi3-win32.whl | CPython 3.11 | abi3 | Windows x86-32 | Details |
| real_regex-2026.9.4-cp311-abi3-musllinux_1_2_x86_64.whl | CPython 3.11 | abi3 | Linux musl 1.2+ x86-64 | Details |
| real_regex-2026.9.4-cp311-abi3-musllinux_1_2_aarch64.whl | CPython 3.11 | abi3 | Linux musl 1.2+ ARM64 | Details |
| real_regex-2026.9.4-cp311-abi3-manylinux_2_24_x86_64.manylinux_2_28_x86_64.whl | CPython 3.11 | abi3 | Linux glibc 2.24+ x86-64, Linux glibc 2.28+ x86-64 | Details |
| real_regex-2026.9.4-cp311-abi3-manylinux_2_24_aarch64.manylinux_2_28_aarch64.whl | CPython 3.11 | abi3 | Linux glibc 2.24+ ARM64, Linux glibc 2.28+ ARM64 | Details |
| real_regex-2026.9.4-cp311-abi3-macosx_11_0_arm64.whl | CPython 3.11 | abi3 | macOS 11.0+ ARM64 | Details |
| real_regex-2026.9.4-cp311-abi3-macosx_10_9_x86_64.whl | CPython 3.11 | abi3 | macOS 10.9+ x86-64 | Details |
Total release size: 19.3 MB
Release files / real_regex-2026.9.4.tar.gz
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