Regular Expressions 101

Save & Share

  • Regex Version: ver. 11
  • Update Regex
    ctrl+⇧+s
  • Save new Regex
    ctrl+s
  • Add to Community Library

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"
"
gsx

Test String

Code Generator

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r""" (?P<content>.*?) # Content up to next tag (?P<markup> # Entire tag <!\[CDATA\[(?P<cdata>.+?)]]>| # <![CDATA[ ... ]]> <!--(?P<comment>.+?)-->| # <!-- Comment --> </\s*(?P<close_tag>\w+)\s*>| # </tag> <(?P<tag>\w+) # <tag ... (?P<attributes> (?P<attribute>\s+ # <snip>: Use this part to get the attributes out of 'attributes' group. (?P<attribute_name>\w+) (?:\s*=\s* (?P<attribute_value> [\w:/.\-]+| # Unquoted (?=(?P<_v> # Quoted (?P<_q>['\"]).*?(?<!\\)(?P=_q))) (?P=_v) ))? # </snip> )* )\s* (?P<is_self_closing>/?) # Self-closing indicator >) # End of tag """ test_str = ("In this case, $url will indeed contain http://example.com/whatever.jpg. But what happens when you start getting HTML like this:\n\n" "<img src='http://example.com/whatever.jpg'>\n" "or\n\n" "<img src=http://example.com/whatever.jpg>\n" "or\n\n" "<img border=0 src=\"http://example.com/whatever.jpg\">\n" "or\n\n" "<img border src=\"http://example.com/whatever.jpg\">\n" "or\n\n" "<img\n" " src=\"http://example.com/whatever.jpg\">\n" "or you start getting false positives from\n\n" "<!-- // commented out\n" "<img src=\"http://example.com/outdated.png\">\n" "-->\n\n" "<script><![CDATA[ This is <b>not</b> parsed ]]></script>\n\n" "<asd ASD=asd>\n\n" "<!-- // commented out <img src=\"http://example.com/outdated.png\"> -->\n\n" "No quotes:\n" "<iframe src=test.html target=xyz></ iframe >\n" "Self-closing tag:\n" "<a href=test.html target=xyz/>\n" "Self closing tag with a space before closure:\n" "<a href=test.html target=xyz />\n" "Double quotes:\n" "<a href=\"test.html\" target=\"xyz\">\n" "Single quotes:\n" "<a href='test.html' target='xyz'>\n" "Escaping double quotes:\n" "<a href=\"test.html?val=1\" title=\"\\\"No rules exist\\\" Andre Breton's quote\">\n" "Escaping single quotes (also with spaces between equals signs):\n" "<a href = \"test.html?val=1\" title = 'Charlie\\'s Angels'>\n" "Tag without closure (ignored):\n" "<a href = \"test.html?val=1\" title='Charlie\\'s Angels'\n" "Tag without opening (ignored):\n" "a href = \"test.html?val=1\" title=\"Charlie\\\"s Angels\">\n\n") matches = re.finditer(regex, test_str, re.DOTALL | re.VERBOSE) 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