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python · re module · raw string · local

Generate Python code from a regex

Drop a JS-style pattern in, pick flags, and get a re module snippet — compile, search, findall, finditer, sub, and split — with raw strings so backslashes stay readable.

Regex → Python
//g
Python
import re

pattern = r"""\\b\\w+@\\w+\\.\\w+\\b"""
flags = 0
text = r"""Reach alice@example.com or bob@test.org."""

regex = re.compile(pattern, flags)

is_match = bool(regex.search(text))
first = regex.search(text)
all_matches = regex.findall(text)
all_iter = list(regex.finditer(text))
replaced = regex.sub(r"""[email]""", text)
parts = regex.split(text)

print({"is_match": is_match, "first": first.group(0) if first else None,
       "all": all_matches, "replaced": replaced, "parts": parts})
Quick Start

How to use a regex in Python

Python's re module uses precompiled Pattern objects via re.compile. Flags are bitfield constants combined with |.

  1. 01

    Type a pattern

    Use a raw string (r"...") to keep backslashes literal — otherwise \b becomes a backspace character before re even sees it.

    Patterns are parsed with the JavaScript RegExp constructor, so syntax errors surface immediately and engine quirks like Unicode property escapes (\p{L}) require the u flag.

    patternECMAScriptliteralregex
    input · literalpattern · regex
    r"\b\w+@\w+\b"
    loaded · ECMAScripttarget · ready
  2. 02

    Tune flags

    JS g, i, m, s, u map to re.IGNORECASE, re.MULTILINE, re.DOTALL, re.UNICODE. Combine with the | bitwise-or.

    Each flag character mirrors the ECMAScript literal: g enables iteration, i folds case, m anchors per line, s lets . match newlines, u unlocks proper Unicode, y is sticky, and d emits indices.

    flagssampleg · i · mlive
    config · optionsflags · flags
    re.I | re.M
    flags applied · livelive · preview
  3. 03

    Read the snippet

    Get compile(), search() (first), findall() (strings), finditer() (Match objects), sub() (replace), and split() in one block.

    The generator rewrites the regex for the target language — handling string-literal escaping, raw-string prefixes, and engine-specific syntax tweaks.

    codegentargetsnippetcopy
    run · outputpreview · code
    regex = re.compile(…)
    snippet · livecode · ready
  4. 04

    Copy code

    One click copies the full snippet — paste into a .py file, a REPL, or a Jupyter cell.

    Copy writes via navigator.clipboard.writeText, so nothing transits the network and the output is byte-identical to what you see on screen.

    copyexportclipboardblob
    export · exportedready · saved
    Copied
    ready to shipsuccess
Pro tips

Regex patterns that don't melt down

Use named groups

(?<year>\d{4}) reads better than $1 and survives reordering. Supported in ECMAScript 2018+.

Anchor strictly

Use ^/$ with the m flag when matching whole lines. Without anchors, partial matches sneak through.

Avoid catastrophic backtracking

Nested quantifiers like (a+)+ can explode. Run patterns through ReDoS Detector first.

Escape every literal

Backslash any meta character you want literally: \.\$\^\*\+\?\(\)\[\]\{\}\|\\.

Test edge cases

Empty string, single character, unicode, the maximum length you expect — write fixtures for each.

Patterns aren&rsquo;t parsers

Don’t parse HTML, JSON, or balanced parens with regex. Use a proper parser when the grammar is recursive.

Related toolsRegex To JavascriptRegex To RubyRegex TesterRegex ExplainerRegex BuilderRegex Replace
Use Cases

When to generate Python regex code

Skip the boilerplate when wiring a pattern into a Django view, a data pipeline, or a CLI.

Data cleaning

Use findall/sub in pandas pipelines to normalise free-text columns. Compiles through the JavaScript RegExp constructor — engine quirks (Unicode property escapes, sticky matching, named groups) work when their flags are on. Error messages cite the exact position of any syntax issue.

ReDoS-safe

Log parsing

Run finditer over log streams to extract every timestamp / IP / ID. Pairs with the ReDoS detector to catch catastrophic backtracking before you deploy. A pattern that handles 1k-character input fine can become a denial-of-service vector on attacker-controlled 1M-character input.

ECMA-compliant

Django form validation

Drop a compiled regex into a Django RegexValidator. Output exports as JavaScript, Python re, Java util.regex, .NET System.Text.RegularExpressions, PCRE, and POSIX — language quirks are highlighted on conversion so you don't ship a JS-only pattern to a Go service.

spec-grade

API filtering

Pre-validate input shape in a FastAPI route before hitting the DB. Capture groups (named or numbered) round-trip cleanly into replacement strings, JSON output, or CSV extraction without re-typing. Backreferences ($1, ${name}) preserve semantics across languages.

cross-engine

Scraping

Pull out structured fields from HTML scraped with requests + BeautifulSoup. Test against edge cases — empty input, single character, max length, multibyte boundaries — to catch off-by-one and zero-length match bugs before they reach production.

test-ready

Notebook EDA

Spin compile/findall into a Jupyter cell for ad-hoc analysis. All matching runs client-side so secret patterns never leave the browser. Useful when the pattern itself is sensitive (PII regexes, internal data formats, security filters).

production-ready
FAQ

Frequently asked questions

Without r"", Python parses \b as a backspace character before re ever sees it. Raw strings preserve the backslashes so the pattern reaches the regex engine intact.
search() looks anywhere in the string. match() only anchors at the start. Use search() unless you specifically need start-anchored behaviour — or just add ^ to your pattern.
findall returns a list of strings (or tuples if there are groups). finditer yields Match objects with .group(), .start(), .span() — what you want when you need positions or named groups.
The third-party regex package (pip install regex) adds Unicode property support, variable-length lookbehinds, and possessive quantifiers. The generated code uses the stdlib re module, but the same syntax works.
No. The code is generated entirely in your browser.
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