Regular Expressions 101

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Function

  • Match
  • Substitution
  • List
  • Unit Tests (9)
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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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r""" ^(?P<timestamp>.{19})\ \[(?P<severity>\w{4,6})\] \ \d+\#\d+:\ (\*\d+\ )? (?P<err_msg> (?:\"\S+\"\sis\snot\s)? (?P<err_type>\w+)[\s(] (?:requests,\ excess:\ (?P<err_rate>\d+\.\d+) \ by\ zone\ \"(?P<err_zone>\S+)\" |.+?) ) (?: ,\ client:\ (?P<remote_addr>\d+\.\d+\.\d+\.\d+) ,\ server:\ (?P<server>[^,\a]+) (?:,\ request:\ \"(?P<method>[A-Z]{3,4}?) \ (?P<uri>\/\S*?)(?P<uri_query>\?\S+)? \ (?P<protocol>\S+)\" )? (?:,\ upstream:\ \"(?P<upstream>.+?)\")? (?:,\ host:\ \"(?P<req_host>\S+)\")? (?:,\ referrer:\ \"(?P<referrer>\S+)\")? |) $ """, flags=re.VERBOSE | re.DOTALL) test_str = ("2023/06/16 17:12:30 [error] 1814859#1814859: *228570402 limiting requests, excess: 50.120 by zone \"resizerzone\", client: 10.5.0.122, server: app.market.com, request: \"GET /resizer/view?key=8e158c8741ce849a09ef84d316bb68e7&b=productimages&f=webp&s=0 HTTP/1.1\", host: \"market.com\", referrer: \"https://market.com/\"\n") match = regex.search(test_str) if match: print(f"Match 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