Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Character class intersection
    [\w&&[^\d]]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"(?<=^|[\n;](?:[\t ]*(?:\w+ )?)?)export\s*(?<modifiers>(?:\s*declare|\s*abstract|\s*async)+)?\s*(?<declaration>class|const +enum|const|enum|function\*?|interface|let|namespace|type(?! *\{)|var)\s+(?<exports>(?:[$_\p{ID_Start}][$\u200C\u200D\p{ID_Continue}]*(?=[\s=:;/({])(?!.*?,))|(?:[\w\t\n\r .,:$'\"=-]+)|(?:[{[][\w\t\n\r .,:$'\"-]+[}\]]))(?:\s*=\s*[$_\p{ID_Start}][$\u200C\u200D\p{ID_Continue}]*)?", flags=re.UNICODE) test_str = ("export const CJS_SYNTAX_REGEX: RegExp = /pattern/gm;export const IGNORE_PATTERNS: string[] = [];\n" "export declare const RESOLVE_EXTENSIONS: string[]\n" "export enum Snack{}\n" "export const enum Snack {}\n" "export interface User {}\n" "export class House {}\n" "export declare abstract class House extends Building {}\n" "export abstract class House {}\n" "export async function run() {}\n" "export async function* run() {}\n" "export function foo() {}\n" "export function* foo() {}\n" "export const $foo = 42\n" "export const $foo= 42\n" "export namespace Foo {}\n" "export type Foo = 'foo'\n" "export let name1, name2/*, … */; // also var\n" "export const name1 = 1, name2 = 2/*, … */; // also var, let\n" "export function functionName() { /* … */ }\n" "export class ClassName { /* … */ }\n" "export function* generatorFunctionName() { /* … */ }\n" "export const { name1, name2: bar } = o;\n" "export const [ name1, name2 ] = array;\n\n" "declare module 'module-name' {\n" " export declare abstract class Building {}\n" " export declare class House extends Building {}\n" "}\n\n" "\"export const $foo = 42\"\n\n" "export default async function functionName() { /* … */ }\n" "export default function functionName() { /* … */ }\n" "export default function* generatorName() { /* … */ }\n" "export default async function* generatorNameAsync() { /* … */ }\n" "export default class ClassName { /* … */ }\n" "export default abstract class ClassName { /* … */ }\n\n" "export default function () { /* … */ }\n" "export default async function () { /* … */ }\n" "export default function* () { /* … */ }\n" "export default async function* () { /* … */ }\n" "export default class { /* … */ }\n\n" "export default async () => {}\n" "export default async arg => {}\n" "export default () => {}\n" "export default arg => {}\n" "export default (arg) => {}\n\n" "export default foo\n" "export default foo;\n" "export default 1 + 1;\n\n" "// export const CJS_SYNTAX_REGEX\n\n" "/**\n" " * Resolvable file extensions.\n" " *\n" " * @example\n" " * export const CJS_SYNTAX_REGEX\n" " */\n\n" "export type Foo = 'foo'") matches = regex.finditer(test_str) for match_num, match in enumerate(matches, start=1): print(f"Match {match_num} was found at {match.start()}-{match.end()}: {match.group()}") for group_num, group in enumerate(match.groups(), start=1): print(f"Group {group_num} found at {match.start(group_num)}-{match.end(group_num)}: {group}")

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Python, please visit: https://docs.python.org/3/library/re.html