Regular Expressions 101

Save & Manage Regex

  • Current Version: 2
  • 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 (4)
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"(?<=\bimport)(\s*(?:[a-z0-9A-Z]+(\s)+)*)((([a-zA-Z0-9]+\.)+)[a-zA-Z0-9]*\*?);") test_str = ("/*\n" "* Copyright 2009 Brian Pellin.\n" "*\n" "* This file is part of KeePassDroid.\n" "*\n" "* KeePassDroid is free software: you can redistribute it and/or modify\n" "* it under the terms of the GNU General Public License as published by\n" "* the Free Software Foundation, either version 2 of the License, or\n" "* (at your option) any later version.\n" "*\n" "* KeePassDroid is distributed in the hope that it will be useful,\n" "* but WITHOUT ANY WARRANTY; without even the implied warranty of\n" "* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the\n" "* GNU General Public License for more details.\n" "*\n" "* You should have received a copy of the GNU General Public License\n" "* along with KeePassDroid. If not, see <http://www.gnu.org/licenses/>.\n" "*\n" "*/\n" "package com.keepassdroid.tests.crypto;\n\n" "import \n" "static \n" "test \n" "test2 \n" "org.junit.Assert.assertArrayEquals.*;\n\n" "import \n" "java.io.IOException;\n" "import java.util.Random;\n\n" "import junit.framework.TestCase;\n\n" "import com.keepassdroid.crypto.finalkey.AndroidFinalKey;\n" "import com.keepassdroid.crypto.finalkey.NativeFinalKey;\n\n" "public class FinalKeyTest extends TestCase {\n" " private Random mRand;\n" " \n" " @Override\n" " protected void setUp() throws Exception {\n" " super.setUp();\n" " \n" " mRand = new Random();\n" " }\n" " \n" " public void testNativeAndroid() throws IOException {\n" " // Test both an old and an even number to test my flip variable\n" " testNativeFinalKey(5);\n" " testNativeFinalKey(6);\n" " }\n" " \n" " private void testNativeFinalKey(int rounds) throws IOException {\n" " byte[] seed = new byte[32];\n" " byte[] key = new byte[32];\n" " byte[] nativeKey;\n" " byte[] androidKey;\n" " \n" " mRand.nextBytes(seed);\n" " mRand.nextBytes(key);\n" " \n" " AndroidFinalKey aKey = new AndroidFinalKey();\n" " androidKey = aKey.transformMasterKey(seed, key, rounds);\n" " \n" " NativeFinalKey nKey = new NativeFinalKey();\n" " nativeKey = nKey.transformMasterKey(seed, key, rounds);\n" " \n" " assertArrayEquals(\"Does not match\", androidKey, nativeKey);\n" " \n" " }\n" "}\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