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"^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$", flags=re.MULTILINE) test_str = ("Valid Semantic Versions\n\n" "0.0.4\n" "1.2.3\n" "10.20.30\n" "1.1.2-prerelease+meta\n" "1.1.2+meta\n" "1.1.2+meta-valid\n" "1.0.0-alpha\n" "1.0.0-beta\n" "1.0.0-alpha.beta\n" "1.0.0-alpha.beta.1\n" "1.0.0-alpha.1\n" "1.0.0-alpha0.valid\n" "1.0.0-alpha.0valid\n" "1.0.0-alpha-a.b-c-somethinglong+build.1-aef.1-its-okay\n" "1.0.0-rc.1+build.1\n" "2.0.0-rc.1+build.123\n" "1.2.3-beta\n" "10.2.3-DEV-SNAPSHOT\n" "1.2.3-SNAPSHOT-123\n" "1.0.0\n" "2.0.0\n" "1.1.7\n" "2.0.0+build.1848\n" "2.0.1-alpha.1227\n" "1.0.0-alpha+beta\n" "1.2.3----RC-SNAPSHOT.12.9.1--.12+788\n" "1.2.3----R-S.12.9.1--.12+meta\n" "1.2.3----RC-SNAPSHOT.12.9.1--.12\n" "1.0.0+0.build.1-rc.10000aaa-kk-0.1\n" "99999999999999999999999.999999999999999999.99999999999999999\n" "1.0.0-0A.is.legal\n\n\n" "Invalid Semantic Versions\n\n" "1\n" "1.2\n" "1.2.3-0123\n" "1.2.3-0123.0123\n" "1.1.2+.123\n" "+invalid\n" "-invalid\n" "-invalid+invalid\n" "-invalid.01\n" "alpha\n" "alpha.beta\n" "alpha.beta.1\n" "alpha.1\n" "alpha+beta\n" "alpha_beta\n" "alpha.\n" "alpha..\n" "beta\n" "1.0.0-alpha_beta\n" "-alpha.\n" "1.0.0-alpha..\n" "1.0.0-alpha..1\n" "1.0.0-alpha...1\n" "1.0.0-alpha....1\n" "1.0.0-alpha.....1\n" "1.0.0-alpha......1\n" "1.0.0-alpha.......1\n" "01.1.1\n" "1.01.1\n" "1.1.01\n" "1.2\n" "1.2.3.DEV\n" "1.2-SNAPSHOT\n" "1.2.31.2.3----RC-SNAPSHOT.12.09.1--..12+788\n" "1.2-RC-SNAPSHOT\n" "-1.0.3-gamma+b7718\n" "+justmeta\n" "9.8.7+meta+meta\n" "9.8.7-whatever+meta+meta\n" "99999999999999999999999.999999999999999999.99999999999999999----RC-SNAPSHOT.12.09.1--------------------------------..12") 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