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]
  • 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

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"((?:if|for|while)\s+?[^:]*?:\n)|(else\s*?:\n)|(else\s+?if[^:]*?:\n)"; string input = @"import datetime import difflib import hashlib import random import re from annoying.functions import get_object_or_None from django.conf import settings from django.contrib.auth.models import User from django.db import models from markdown_deux import markdown from pygments import highlight from pygments.formatters import HtmlFormatter from pygments.lexers import get_lexer_by_name from pygments.util import ClassNotFound from snipts.utils import slugify_uniquely from taggit.managers import TaggableManager from taggit.utils import edit_string_for_tags from teams.models import Team class Snipt(models.Model): """"An individual Snipt."""" user = models.ForeignKey(User, blank=True, null=True, on_delete=models.CASCADE) last_user_saved = models.ForeignKey( User, blank=True, null=True, related_name=""last_user_saved"", on_delete=models.CASCADE, ) title = models.CharField(max_length=255, blank=True, null=True, default=""Untitled"") slug = models.SlugField(max_length=255, blank=True) custom_slug = models.SlugField(max_length=255, blank=True) tags = TaggableManager() lexer = models.CharField(max_length=50) code = models.TextField() meta = models.TextField(blank=True, null=True) description = models.TextField(blank=True, null=True) stylized = models.TextField(blank=True, null=True) stylized_min = models.TextField(blank=True, null=True) embedded = models.TextField(blank=True, null=True) line_count = models.IntegerField(blank=True, null=True, default=None) key = models.CharField(max_length=100, blank=True, null=True) public = models.BooleanField(default=False) secure = models.BooleanField(default=False) blog_post = models.BooleanField(default=False) views = models.IntegerField(default=0) created = models.DateTimeField(auto_now_add=True, editable=False) modified = models.DateTimeField(auto_now=True, editable=False) publish_date = models.DateTimeField(blank=True, null=True) def _unidiff_output(self, expected, actual): expected = expected.splitlines(1) actual = actual.splitlines(1) diff = difflib.unified_diff(expected, actual) return "".join(diff) def __init__(self, *args, **kwargs): super(Snipt, self).__init__(*args, **kwargs) self.original_code = self.code def save(self, *args, **kwargs): if not self.slug: self.slug = slugify_uniquely(self.title, Snipt) if not self.key: self.key = hashlib.md5( ( self.slug + str(datetime.datetime.now()) + str(random.random()) ).encode(""utf-8"") ).hexdigest() if self.lexer == ""markdown"": self.stylized = markdown(self.code, ""default"") # Snipt embeds for match in re.findall('\[\[(\w{32})\]\]', self.stylized): self.stylized = self.stylized.replace('[[' + str(match) + ']]', """" <script type=""text/javascript"" src=""https://snipt.net/embed/{}/?snipt""> </script> <div id=""snipt-embed-{}""></div>"""".format( match, match ), ) # YouTube embeds for match in re.findall( ""\[\[youtube-(\w{11})\-(\d+)x(\d+)\]\]"", self.stylized ): self.stylized = self.stylized.replace( ""[[youtube-{}-{}x{}]]"".format( str(match[0]), str(match[1]), str(match[2]) ), """"<iframe width=""{}"" height=""{}"" src=""https://www.youtube.com/embed/{}"" frameborder=""0"" allowfullscreen></iframe>"""".format( match[1], match[2], match[0] ), ) # Vimeo embeds for match in re.findall(""\[\[vimeo-(\d+)\-(\d+)x(\d+)\]\]"", self.stylized): self.stylized = self.stylized.replace( ""[[vimeo-{}-{}x{}]]"".format( str(match[0]), str(match[1]), str(match[2]) ), """"<iframe src=""https://player.vimeo.com/video/{}"" width=""{}"" height=""{}"" frameborder=""0"" webkitAllowFullScreen mozallowfullscreen allowFullScreen></iframe>"""".format( match[0], match[1], match[2] ), ) # Tweet embeds for match in re.findall(""\[\[tweet-(\d+)\]\]"", self.stylized): self.stylized = self.stylized.replace( ""[[tweet-{}]]"".format(str(match)), '<div class=""embedded-tweet"" data-tweet-id=""{}""></div>'.format( str(match) ), ) # Parse Snipt usernames for match in re.findall('@(\w+) ', self.stylized): # Try and get the Snipt user by username. user = get_object_or_None(User, username=match) if user: url = user.profile.get_user_profile_url() self.stylized = self.stylized.replace( ""@{} "".format(str(match)), '<a href=""{}"">@{}</a> '.format(url, match), ) else: self.stylized = highlight( self.code, get_lexer_by_name(self.lexer, encoding=""UTF-8""), HtmlFormatter( linenos=""table"", anchorlinenos=True, lineanchors=""L"", linespans=""L"" ), ) self.line_count = len(self.code.split(""\n"")) if self.lexer == ""markdown"": lexer_for_embedded = ""text"" else if asdgh: asd else: lexer_for_embedded = self.lexer embedded = highlight( self.code, get_lexer_by_name(lexer_for_embedded, encoding=""UTF-8""), HtmlFormatter( style=""native"", noclasses=True, prestyles="""" background-color: #1C1C1C; border-radius: 5px; color: #D0D0D0; display: block; font: 11px Monaco, monospace; margin: 0; overflow: auto; padding: 15px; -webkit-border-radius: 5px; -moz-border-radius: 5px; """", ), ) embedded = ( embedded.replace('\\""', '\\\\""') .replace(""'"", ""\\'"") .replace(""\\"", ""\\\\"") .replace(""background: #202020"", "") ) self.embedded = embedded snipt = super(Snipt, self).save(*args, **kwargs) diff = self._unidiff_output(self.original_code or "", self.code) if diff != "": log_entry = SniptLogEntry( user=self.last_user_saved, snipt=self, code=self.code, diff=diff ) log_entry.save() return snipt def __unicode__(self): return self.title def favs(self): return Favorite.objects.filter(snipt=self).count() def get_stylized_min(self): if self.stylized_min is None: if self.lexer == ""markdown"": self.stylized_min = markdown(self.code[:1000], ""default"") else: self.stylized_min = highlight( self.code[:1000], get_lexer_by_name(self.lexer, encoding=""UTF-8""), HtmlFormatter(linenos=""table"", linenospecial=1, lineanchors=""line""), ) return self.stylized_min def get_absolute_url(self): if self.blog_post: if self.user.profile.blog_domain: return u""http://{}/{}/"".format( self.user.profile.blog_domain.split("" "")[0], self.slug ) else: return u'https://{}.snipt.net/{}/'.format( self.user.username.replace('_', '-'), self.slug) if self.custom_slug: return u""/{}/"".format(self.custom_slug) if self.public: return u""/{}/{}/"".format(self.user.username, self.slug) else: return u""/{}/{}/?key={}"".format(self.user.username, self.slug, self.key) def get_full_absolute_url(self): if self.blog_post: if self.user.profile.blog_domain: return u""http://{}/{}/"".format( self.user.profile.blog_domain.split("" "")[0], self.slug ) else: return u'https://{}.snipt.net/{}/'.format( self.user.username, self.slug) if self.public: return u""/{}/{}/"".format(self.user.username, self.slug) else: return u""/{}/{}/?key={}"".format(self.user.username, self.slug, self.key) def get_download_url(self): try: lexer_obj = get_lexer_by_name(self.lexer) except ClassNotFound: lexer_obj = None if lexer_obj and lexer_obj.filenames: filename = lexer_obj.filenames[0].replace(""*"", self.slug) else: if self.lexer == ""markdown"": filename = u""{}.md"".format(self.slug) else: filename = u""{}.txt"".format(self.slug) return u""/download/{}/{}"".format(self.key, filename) def get_embed_url(self): if settings.DEBUG: root = 'http://local.snipt.net' else: root = 'https://snipt.net' return ""{}/embed/{}/"".format(root, self.key) def get_raw_url(self): return ""/raw/{}/"".format(self.key) @property def sorted_tags(self): return self.tags.all().order_by(""name"") @property def tags_list(self): return edit_string_for_tags(self.tags.all()) @property def lexer_name(self): if self.lexer == ""markdown"": return ""Markdown"" else: return get_lexer_by_name(self.lexer).name def is_authorized_user(self, user): if self.user == user: return True if self.user.profile.is_a_team: team = Team.objects.get(user=self.user, disabled=False) return team.user_is_member(user) return False class SniptLogEntry(models.Model): """"An individual log entry for a Snipt changeset."""" user = models.ForeignKey(User, on_delete=models.CASCADE) snipt = models.ForeignKey(Snipt, on_delete=models.CASCADE) code = models.TextField() diff = models.TextField() created = models.DateTimeField(auto_now_add=True, editable=False) modified = models.DateTimeField(auto_now=True, editable=False) @property def snipt_name(self): return self.snipt.title or ""Untitled"" class SniptSecureView(models.Model): """"A single view to a secure snipt."""" user = models.ForeignKey(User, on_delete=models.CASCADE) snipt = models.ForeignKey(Snipt, on_delete=models.CASCADE) created = models.DateTimeField(auto_now_add=True, editable=False) modified = models.DateTimeField(auto_now=True, editable=False) @property def snipt_name(self): return self.snipt.title or ""Untitled"" class Favorite(models.Model): snipt = models.ForeignKey(Snipt, on_delete=models.CASCADE) user = models.ForeignKey(User, on_delete=models.CASCADE) created = models.DateTimeField(auto_now_add=True, editable=False) modified = models.DateTimeField(auto_now=True, editable=False) def __unicode__(self): return u""{} favorited by {}"".format(self.snipt.title, self.user.username) "; foreach (Match m in Regex.Matches(input, pattern)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx