Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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]
  • 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
No Match

r"
"
g

Test String

Code Generator

Language

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r"<!DOCTYPE html>|</?\s*[a-z-][^>]*\s*>|(\&(?:[\w\d]+|#\d+|#x[a-f\d]+);|<!--[\s\S\n]*?-->)" test_str = ("\n" "# Above is a blank line, no match.\n\n" "foo bar baz\n" "this is a string\n" "Testing\n" "<>\n" "Hello, World\n" "This is less than <, this is greater than >.\n" " a < 3 && b > 3\n" "<<Important Text>>\n" "# Not HTML-like.\n\n" "<p>fizz buzz</p>\n" "<a>this is a string</a>\n" "this is a <b>string</b>\n" "<p>Testing</p>\n" "<img src=\"hello.jpg\">\n" "<a>Foo</a>\n" "<input type='submit' value='Ok' />\n" "<input type='submit' value='Ok'>\n" "<br/>\n" "<br>\n" "<!-- comment -- doesn't work! -->\n" "<hr>\n" "Foo &amp; bar\n" "# These one-line samples are totally HTML-like.\n\n" "<file-upload>\n" "<absurd example>\n" "<closed example></closed>\n" "# Custom tags.\n\n" "<a>\n" "# Not matched by others, but actually valid.\n\n" "My < weird > string\n" "# Not actually a false positive; this is valid HTML!\n\n" "# Sample \"smallest complete HTML document\":\n" "<!DOCTYPE html>\n" "<title>testing</title>\n" "<p>This is a test.</p>\n" "<strange>This is strange.</strange>\n" "# And yes, <strange> IS VALID HTML.\n\n" "résume\n" "r&eacute;sume\n" "r&#201;sume\n" "r&x00C9;sume\n" "# Entities\n\n" "# List Tricks\n" "<ul><li>Foo</li\n" "><li>Bar</li\n" "></ul>\n\n" "# From https://stackoverflow.com/a/51325984/211827\n" "Hello, World\n" "This is less than <, this is greater than >.\n" " a < 3 && b > 3\n" "<<Important Text>>\n" "<a> # This actually is HTML, not a false positive.\n" "<a>Foo</a>\n" "<input type='submit' value='Ok' /> # XHTML, not HTML...\n" "<br/> # XHTML again...\n" "<br> # These didn't work with that answer.\n" "Foo &amp; bar\n" "<input type='submit' value='Ok'>\n\n" "# From https://regex101.com/r/cX0eP2/1\n" "<a href=bla>sdfsdf</a>\n" "<div>something</div>\n" "<br>\n" "<span>mayhem</div>\n" "<hr />\n" "<input name=bla / >\n" "<div>some<span>thing</span>here</div>\n\n\n" "# Prepare your eye bleach.\n" "<p style=\"line-height:normal; margin-top:0px\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Notre sp&eacute;cialit&eacute; : offrir de l&rsquo;assistance &agrave; plus d&rsquo;un million de Qu&eacute;b&eacute;cois. Nous sommes fiers d&rsquo;aider! Participez vous aussi &agrave; cette mission en r&eacute;alisant les r&ecirc;ves d&rsquo;aventure, de d&eacute;tente et de d&eacute;couverte de nos membres et clients au sein de notre agence de voyages.</span></span></p>\\r\\n\\r\\n<p style=\"line-height:normal; margin-top:0px\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Joignez-vous &agrave; nous! Vous b&eacute;n&eacute;ficierez de nombreux avantages :&nbsp;</span></span></p>\\r\\n\\r\\n<ul style=\"line-height:normal\">\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Salaire fixe, et primes lorsque vous d&eacute;passez vos objectifs.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">20 jours de cong&eacute; apr&egrave;s une ann&eacute;e.</span></span></li>\\r\\n\\t<li><span style=\"font-size:12px\"><span style=\"font-family:Arial\">R&eacute;gime de retraite - CAA-Qu&eacute;bec &eacute;gale votre mise!</span></span></li>\\r\\n\\t<li><span style=\"font-size:12px\"><span style=\"font-family:Arial\">Assurance collective compl&egrave;te (soins m&eacute;dicaux et param&eacute;dicaux, invalidit&eacute;, etc.).</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Rabais trippants chez nos partenaires, dans nos centres Voyages et pour vos assurances.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Plus de 1,2 million de membres comme clients potentiels.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Soutien administratif pour vous concentrer sur la vente de voyages.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Allocation g&eacute;n&eacute;reuse pour les &eacute;ducotours.</span></span></li>\\r\\n</ul>\\r\\n\\r\\n<p style=\"line-height:normal; margin-bottom:0px; margin-top:0px\">&nbsp;</p>\\r\\n\\r\\n<p style=\"line-height:normal; margin-bottom:0px; margin-top:0px\"><img class=\"largeimage\" src=\"https://gestiondestalents.caaquebec.com/caa/login/caa/_attachments/news_files/activex/image%20conseiller%20en%20voyage.JPG\" style=\"line-height:normal; width:100%\" /></p>\\r\\n\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t <br/><br/>\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t<p style=\"line-height:normal; margin-top:0px\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">En tant que conseiller en voyages, vos principales t&acirc;ches et responsabilit&eacute;s seront celles-ci :</span></span></p>\\r\\n\\r\\n<ul style=\"line-height:normal\">\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">R&eacute;aliser une analyse des besoins des clients et leur fournir des renseignements pr&eacute;cis et utiles.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Effectuer les r&eacute;servations et achats (forfaits, croisi&egrave;res, circuits, h&ocirc;tels, automobiles et assurances voyage).</span></span></li>\\r\\n</ul>\\r\\n\\r\\n<p style=\"line-height:normal; margin-top:0px\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Vous occuperez un poste r&eacute;gulier &agrave; temps plein (35&nbsp;heures par semaine). L&rsquo;horaire sera variable et vous devrez parfois travailler le soir et la fin de semaine afin de bien servir les voyageurs.</span></span></p>\\r\\n\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t\\r\\n\\t\\t <br/><br/>\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t\\t<p style=\"line-height:normal; margin-top:0px\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Nous sommes toujours &agrave; la recherche de personnes de talent. Mais vous devrez avoir un profil pr&eacute;cis pour ce poste!</span></span></p>\\r\\n\\r\\n<ul style=\"line-height:normal\">\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Dipl&ocirc;me d&rsquo;&eacute;tudes coll&eacute;giales en tourisme ou formation d&rsquo;agent de voyages.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">2 &agrave; 3 ann&eacute;es d&rsquo;exp&eacute;rience comme conseiller en voyages.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Certificat de conseiller en voyages de l&rsquo;Office de la protection du consommateur, ou &ecirc;tre en mesure de l&rsquo;obtenir.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Connaissance des syst&egrave;mes de d&eacute;livrance de billets : GDS, Galileo/Apollo, PcVoyages et SIREV (un atout).</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Ma&icirc;trise du fran&ccedil;ais et de l&rsquo;anglais.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Professionnalisme, attention aux besoins des clients et volont&eacute; d&rsquo;offrir un service de qualit&eacute;.</span></span></li>\\r\\n\\t<li style=\"line-height: normal;\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\">Souci d&rsquo;atteindre les objectifs de vente.</span></span></li>\\r\\n</ul>\\r\\n\\r\\n<p style=\"line-height:normal; margin-top:0px\"><span style=\"font-size:12px; line-height:normal\"><span style=\"font-family:Arial; line-height:normal\"><span style=\"line-height:normal\">Si explorer de nouveaux horizons vous passionne, et que vous aimez aider d&rsquo;autres personnes &agrave; d&eacute;couvrir le monde, vous serez heureux &agrave; Voyages CAA-Qu&eacute;bec. Postulez d&egrave;s aujourd&rsquo;hui. Nous vous attendons avec impatience!</span></span></span></p>") matches = re.finditer(regex, test_str) for matchNum, match in enumerate(matches, start=1): print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group())) for groupNum in range(0, len(match.groups())): groupNum = groupNum + 1 print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum))) # Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

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