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]{0,2}\[([\d]*)\]:", flags=re.MULTILINE) test_str = ("---\n" " # Meta Data\n" " Title: Test Set for Mark Down Reference Linking\n" " Summary: Test Set for Mark Down Reference Linking\n" " Author: Royi \n\n" " # Settings\n" " settings:\n" " enable_uml: true\n" " image_path_conversion: base64\n" " markdown_extensions:\n" " - markdown.extensions.footnotes\n" " - markdown.extensions.fenced_code\n" " - markdown.extensions.tables\n" " - markdown.extensions.admonition\n" " - markdown.extensions.toc:\n" " title: Table of Contents\n" " toc_depth: 2-3\n" " - pymdownx.arithmatex:\n" " generic: true\n" " smart_dollar: false\n" " allow_css_overrides: true\n" "---\n\n\n" "# Test Set for Mark Down Reference Linking\n\n" "[TOC]\n\n" "## Scope of the Document\n\n" "Just some text as a test set.\n\n\n" "### Some ASCII Graphics\n\n" "Laser beam.\n\n" "```\n" " \n" " Target \n" " \n" " +--------------------------------+ \n" " | | \n" " | | \n" " | | \n" " | | \n" " | -- | \n" " | -/ | \n" " | --/ | \n" " | -/ | \n" " | --/ | \n" " +--------------------------------+ \n" " -/ \n" " --/ \n" " <-------------------/-----------------------> \n" " --/ \n" " -/ \n" " --/ \n" " +--------/ \n" " | -/| \n" " | -/ | \n" " | | Laser Beam\n" " +------+ \n" "```\n\n" "## Some List\n\n" " * Train Set - Set used for training the ML model (For instance optimize the model parameters [For Parametric Model])\n" " * Test Set - Set used to evaluate results.\n" " * Prediction - Prediction of velocity given a measurement.\n\n" "Implicit / Explicit Assumptions[^001]:\n\n" " * The laser beam is eye safe.\n" " * Just some information[^002].\n\n" "### Some Existing Links\n\n" "The results are pretty good in [RMSE][001] / [MAE][002].\n\n\n" "## Some Text to Test\n\n" "Free text, **bold text**, *italic text*, [__bold text__][003] or _italic text_.\n" "Also, `Mono Spaced Text` and regular [boring text][04].\n\n" "Some [Link](https://www.wikipedia.com) and [Reference Link][1].\n\n" "Some list...\n\n" " * Examining Deep Learning (DL) Based Methods \n" " Always some text on [Deep][1] Learning.\n" " * Hyper Parameters \n" " Adding an exhaustive search of the optimal Hyper Parameters.\n\n\n" " [001]: https://en.wikipedia.org/wiki/Root-mean-square_deviation \"Wikipedia - RMSE\"\n" " [002]: https://en.wikipedia.org/wiki/Mean_absolute_error \"Wikipedia - MAE\"\n\n" "[003]: https://something.com\n" " [04]: https://somewhere.com\n\n" " [5]: Should not be selected!\n" " [6]: Should not be selected!\n\n\n" " [^001]: Just a simple assumption reference.\n" " [^002]: Just another simple assumption reference.\n\n\n\n\n" "[1]: https://www.wikipedia.com") 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