Regular Expressions 101

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  • Unit Tests (18)

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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

/
/
g

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"\b(?:(25[0-5]|2[0-4][0-9]|[01]?[0-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|[01]?[0-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|[01]?[0-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|[01]?[0-9]?[0-9]))\b" test_str = ("This REGULAR EXPRESSION is just for searching for dotted decimal IPv4 Adresses.\n" "Unlike a shorter one, this one is made for seeing the numbers in seperate Mach-groups-thingy.\n" "I also included some unit tests.. But i think they are not needed.\n\n" "Below are some tests:\n\n" "Valid:\n" "0.0.0.0\n" "1.2.3.4\n" "127.0.0.1\n" "8.8.4.4\n" "8.8.8.8\n" "255.255.255.255\n" "249.0.0.1\n" "0.1.255.254\n" "98.139.180.149\n" "69.89.31.226\n\n\n" "Invalid:\n" "999.999.999\n" "290.250.2.6\n" "256.259.20.255\n\n\n" "Texts:\n" "Google DNS Server IP is 8.8.8.8. As a alternative you can use 8.8.4.4. \n" "The IP 127.0.0.1 (also known as localhost) is a 'loopback' IP-Adress, pointing to your computer.\n\n\n" "Example pinging:\n" " Microsoft Windows [Version 6.1.7601]\n" " Copyright (c) 2009 Microsoft Corporation. Alle Rechte vorbehalten.\n" " \n" " C:\\Users\\Example>ping google.com\n" " \n" " Pinging google.com [212.6.83.44] with 32 bytes of data:\n" " Reply from 212.6.83.44: bytes=32 time=42ms TTL=59\n" " Reply from 212.6.83.44: bytes=32 time=55ms TTL=59\n" " Reply from 212.6.83.44: bytes=32 time=35ms TTL=59\n" " Reply from 212.6.83.44: bytes=32 time=27ms TTL=59\n" " \n" " Ping statistics for 212.6.83.44:\n" " Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),\n" " Approximate round trip times in milli-seconds:\n" " Minimum = 27ms, Maximum = 55ms, Average = 39ms\n" " \n" " C:\\Users\\Example>") matches = re.finditer(regex, test_str) 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