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 (4)

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

/
/
gm

Test String

Substitution

Processing...

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"^([ \t]*)import [*] as (\w+) from (?:(['])((?:(?:\.)+|[^\n\r'\\]+)+)[']|([\"])((?:(?:\.)+|[^\n\r'\\]+)+)[\"])" test_str = ("import * as Atblock from \"./atblock\"\n" "import * as Atrule from \"./atrule\"\n" "import * as Supports from \"./supports\"\n\n" "import * as Node from './node';\n" "import * as Root from './root'\n" "import Null from './null'\n" "import * as Each from './each'\n" "import * as If from './if'\n" "import * as Call from './call'\n" "import * as UnaryOp from './unaryop'\n" "import * as BinOp from './binop'\n" "import * as Ternary from './ternary'\n" "import * as Block from './block'\n" "import * as Unit from './unit'\n" "import * as String from './string'\n" "import * as HSLA from './hsla'\n" "import * as RGBA from './rgba'\n" "import * as Ident from './ident'\n" "import * as Group from './group'\n" "import * as Literal from './literal'\n" "import * as Boolean from './boolean'\n" "import * as Return from './return'\n" "import * as Media from './media'\n" "import * as QueryList from './query-list'\n" "import * as Query from './query'\n" "import * as Feature from './feature'\n" "import * as Params from './params'\n" "import * as Comment from './comment'\n" "import * as Keyframes from './keyframes'\n" "import * as Member from './member'\n" "import * as Charset from './charset'\n" "import * as Namespace from './namespace'\n" "import * as Import from './import'\n" "import * as Extend from './extend'\n" "import * as Object from './object'\n" "import * as Function from './function'\n" "import * as Property from './property'\n" "import * as Selector from './selector'\n" "import * as Expression from './expression'\n" "import * as Arguments from './arguments'\n" "import * as Atblock from './atblock'\n" "import * as Atrule from './atrule'\n" "import * as Supports from './supports'\n") subst = "$1import $2 from $3$5$6$4$3$5" # You can manually specify the number of replacements by changing the 4th argument result = re.sub(regex, subst, test_str, 0, re.MULTILINE) if result: print (result) # 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