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

/
/
gm

Test String

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"(?-i)^[\t ]*((?:[!(]|\w+\(|(?:(?:const|let|var)[\t ]+)?[\w$]+[\t ]*[:=][\t ]*(?:{\w+[\t ]*:[\t ]*)?)?)((?:\([^\r\n)]*\)|\w)[\t ]*=>)" test_str = ("!function(){}(); // test1\n" "!function test2(){}(); // test2\n" "(function(){})(); // test3\n" "(function test4(){})(); // test4\n" "test5 = function(){} // test5\n" "test6 = function _test6(){} // test6\n" "let test7 = function(){} // test7\n" "let test8 = function _test8(){} // test8\n" "var test9 = function(){} // test8\n" "var test10 = function _test10(){} // test10\n" "const test11 = function(){} // test11\n" "const test12 = function _test12(){} // test12\n" "myfunc(function(){}) // test13\n" "myfunc(function test14(){}) // test14\n" "let myobj15 = {test15 : function(){}} // test15\n" "let myobj16 = {test16 : function _test16(){}} // test16\n" "var myobj17 = {test17 : function(){}} // test17\n" "var myobj18 = {test18 : function _test18(){}} // test18\n" "const myobj19 = {test19 : function(){}} // test19\n" "const myobj20 = {test20 : function _test20(){}} // test20\n" "!function(a){}(); // test21\n" "!function test22(b){}(); // test22\n" "(function(c){})(); // test23\n" "(function test24(d){})(); // test24\n" "test25 = function(e){} // test25\n" "test26 = function _test26(f){} // test26\n" "let test27 = function(g){} // test27\n" "let test28 = function _test28(h){} // test28\n" "var test29 = function(i){} // test29\n" "var test30 = function _test30(j){} // test30\n" "const test31 = function(k){} // test31\n" "const test32 = function _test32(l){} // test32\n" "myfunc(function(m){}) // test33\n" "myfunc(function test34(n){}) // test34\n" "let myobj35 = {\n" " test35 : function(o){} // test35\n" "}\n" "let myobj36 = {\n" " test36 : function _test36(p){} // test36\n" "}\n" "var myobj37 = {\n" " test37 : function(q){} // test37\n" "}\n" "var myobj38 = {\n" " test38 : function _test38(r){} // test38\n" "}\n\n" "test39 = () => {} // test39\n" "test40 = v => {} // test40\n" "test41 = (w) => {} // test41\n" "test42 = (x,y) => {} // test42\n\n" "let test43 = v => {} // test43\n" "var myobj44 = {test44 : (w) => {}} // test44\n" "const myobj45 = {\n" " test45 : (x,y) => {} // test45\n" "}\n" "myfunc(() => {}) // test46\n" "myfunc(v => {}) // test47\n\n" "function test48(){} // test48\n" "function test49(s){} // test49\n" "function test50(t,u){} // test50") matches = re.finditer(regex, test_str, re.MULTILINE) 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