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"^(?<event>\d+-\d+-\d+\s+\d+:\d+:\d+,\d+\s(ERROR|SEVERE).*)" test_str = ("2021-08-31 02:03:52,081 INFO [stdout] jkwqdwqjdk\n" "2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83)\n" "2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83) Abc fgh, app continuing\n" "2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83)\n\n" "2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83)kwqskqw\n" "2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83)\n" "2021-08-31 02:03:52,081 INFO [org.kjskj.akjs] (ServerService Thread Pool -- 11) WFLYUT0021: Registered web context: '/dyn' for server 'default-server'\n" "2021-08-31 02:03:52,081 ERROR [org.kjskj.akjs] \"There is an error\"\n" "2021-08-31 02:03:52,081 SEVERE [org.kjskj.akjs] There is Severe\n" "2021-08-31 02:03:55,166 INFO [org.jboss.as] (Controller Boot Thread) WAAAAAA0033: JBoss EAP 1.1.9.GA (abcfegc Core 2.0.10.Final-call-00000) started in 169999ms - Started 2222 of 2222 services (311 services are lazy, passive or on-demand)\n" "2021-08-31 02:03:55,169 INFO [org.jboss.as] (aa nnnThread) WAAAAAA0033: Http interface listening on http://111.11.11.11:8080/aaa\n" "2021-08-31 02:03:55,169 INFO [org.nnn.as] (ioio llkl Thread) WAAAAAA0033: console listening on http://111.11.11.11:8080/aaa") 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