Regular Expressions 101

Save & Manage Regex

  • Current Version: 1
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"[^\w](?<!->)(trans|trans_choice|Lang::get|Lang::choice|Lang::trans|Lang::transChoice|@lang|@choice|__)\s*\(\s*((?<![\\])['\"])((?:.(?!(?<![\\])\2))*.?)\2\s*[,\)]") test_str = ("Should match variations on method:\n" "trans('a.b');\n" "trans_choice('a.b')\n" "Lang::get('a.b');\n" "Lang::choice('a.b', 1);\n" "Lang::trans('a.b');\n" "Lang::transChoice('a.b', 2);\n" "@lang('language.line')\n" "@choice('language.line', 1);\n" "__('a.b')\n\n" "Should match variations of contained string\n" "trans('key'); // No group, so JSON style\n" "__('Json string')\n" "trans('a.b');\n" "trans('a.b.c');\n" "trans('a_b.c-d');\n" "trans('a.b!');\n" "trans('a.translate me!');\n" "trans('a.über~');\n" "trans(\"app.i'm\"); // contained quote of different type\n" "trans('app.\"ok\"');\n" "trans('with contained \" quotes');\n" "trans('with an escaped \\' quote')\n" "trans('with a double \\\\')\n\n" "Should match additional variables and whitespace\n" "trans('a.b', [1,2]);\n" "trans ( \n" " ' with whitespace ' , $var)\n\n" "Typical use cases\n" "(trans ( 'lang.line'));\n" "<span>@lang('lang.line')</span>\n\n" "Should not match:\n" "trans($var); // No quotes\n" "trans(); // Nothing\n" "anytrans('group.key'); // not the method we need\n" "1trans('lang.file'); // not the method\n" "_trans('lang.file'); // not the method\n" "->trans('lang.line');\n" "trans(\\'why do we have an escaped quote here?\\')\n" "trans('with a triple \\\\\\') <-- fail!\n" "trans('lang.line' . $middle); // concatenated vars\n" "trans('lang.line' . $middle . '.ending'); // concatenated vars\n" "___('hello') // not the method we need\n") 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