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

Substitution
Processing...

Code Generator

Language

Generated Code

import re regex = re.compile(r"(?<!\s)(?<!since)(\s*)1\.0\.0", flags=re.MULTILINE) test_str = ("/**\n" " * @since 1.0.0 <--- this shouldn't be matched\n" " * @package blah blah blah\n" " * Version: 1.0.0 <--- this should be matched\n" " */\n\n" "/**\n" " * Fired during plugin activation.\n" " *\n" " * This class defines all code necessary to run during the plugin's activation.\n" " *\n" " * @since 1.0.0 <--- this shouldn't be matched\n" " * @package blah blah\n" " * @subpackage blah blah\n" " * @author blah blah\n" " */\n\n" "define( 'PLUGIN_VERSION', '1.0.0' ); // <--- this should be matched\n") subst = "${1}1.2.3" result = regex.sub(subst, test_str) if result: print(result)

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