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"box(?!-shadow) ") test_str = ("positive lookahead\n" "box(?=-shadow)\n\n" "https://youtu.be/aIEjh0YsxWA?t=309\n" "// select box only if what comes after it IS -shadow\n\n" "box-sizing\n" "shape-shadow\n" "------------------------------------------------------------------\n" "negative lookahead\n" "box(?!-shadow) \n\n" "// select box only if what comes after it IS NOT shadow\n\n" "box-sizing\n" "shape-shadow\n\n" "------------------------------------------------------------------\n" "negative look behind\n" "(?<!jeffery).+\n\n" "https://youtu.be/aIEjh0YsxWA?t=212\n" "// this string cannot come before the @\n\n" "jeffrey@envato.com\n" "joe@envato.com\n\n" "------------------------------------------------------------------\n" "positive look behind\n" "(?<=box-)sizing\n\n" "https://youtu.be/aIEjh0YsxWA?t=337\n" "// only want to select 'sizing' if what comes before it is 'box' \n" "// select sizing as long as what comes before it is 'box'\n\n" "box-sizing\n" "shape-sizing\n\n" "------------------------------------------------------------------\n\n" "negative look behind\n" "(?<!box-)sizing\n\n" "// anything can come before it except 'box'\n\n" "box-sizing\n" "shape-sizing\n\n" "-----------------------------------------------------------------\n" "positive lookahead \n" "@.+(?=\\.[a-z]{2,4})\n\n" "// Matches a group after your main expression without including it in the result\n\n" "wilson@gmail.com\n" "frank@france.fr\n" "joe@paris.france\n\n") 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