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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile((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"), flags=re.IGNORECASE | re.MULTILINE) 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 = regex.finditer(test_str) for match_num, match in enumerate(matches, start=1): print(f"Match {match_num} 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