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

/
/
igm

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"(?:^|\s)(([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]+|::(ffff(:0{1,4})?:)?((25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d)|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d))(?=\s|$)\n") test_str = ("{1: Initial address, regex should say valid/match}\n" "2001:0db8:0000:0000:0000:ff00:0042:8329\n\n" "{2: After removing all leading zeroes, regex should say valid/match}\n" "2001:db8:0:0:0:ff00:42:8329\n\n" "{3: After omitting consecutive sections of zeroes, regex should say valid/match}\n" "2001:db8::ff00:42:8329\n\n" "{4: The loopback address, regex should say valid/match}\n" "0000:0000:0000:0000:0000:0000:0000:0001\n\n" "{5: The loopback address be abbreviated to ::1 by using both rules, regex should say valid/match}\n" "::1\n\n" "{6: This should be valid, regex should say valid/match}\n" "ABCD:ABCD:ABCD:ABCD:ABCD:ABCD:192.168.158.190\n\n" "{7: This should NOT be valid/match}\n" "::\n\n" "{These two formats allows IPv6 applications to communicate directly with IPv4 applications, regex should say valid/match}\n" "{8}\n" "0:0:0:0:0:ffff:192.1.56.10\n" "{9}\n" "::ffff:192.1.56.10/96\n\n" "{These next two formats are used for tunneling. It allows IPv6 nodes to communicate across an IPv4 infrastructure, regex should say valid/match}\n" "{10}\n" "0:0:0:0:0:0:192.1.56.10\n" "{11}\n" "::192.1.56.10/96\n\n" "{These 4 should be valid/match}\n" "{12}\n" "::FFFF:129.144.52.38\n" "{13}\n" "::129.144.52.38\n" "{14}\n" "::FFFF:d\n" "{15}\n" "1080:0:0:0:8:800:200C:417A\n\n" "{These 4 should NOT be valid/match}\n" "{16}\n" "::FFFF:d.d.d\n" "{17}\n" "::FFFF:d.d\n" "{18}\n" "::d.d.d\n" "{19}\n" "::d.d") matches = re.finditer(regex, test_str, re.IGNORECASE | 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