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
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Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"@(?P<citekey>\w[\w:.#$%&\-+?<>~/]*\w+)", flags=re.MULTILINE) test_str = ("The [Pandoc manual](https://pandoc.org/MANUAL.html#citations) defines the following syntax for citation keys:\n\n" "> The citation key must begin with a letter, digit, or `_`, and may contain alphanumerics, `_`, and internal punctuation characters (`:.#$%&-+?<>~/`). Here are some examples:\n\n" "## Valid citekeys\n\n" "Manubot supports citations like `@source:identifier`, where `source` is one of the options described below. The citekeys in this section are valid according to the Pandoc syntax.\n\n" "1. DOI (Digital Object Identifier), cite like `@doi:10.15363/thinklab.4`.\n" " Shortened versions of DOIs can be created at [shortdoi.org](http://shortdoi.org/).\n" " shortDOIs begin with `10/` rather than `10.` and can also be cited.\n" " For example, Manubot will expand `@doi:10/993` to the DOI above.\n" " We suggest using shortDOIs to cite DOIs containing forbidden characters, such as `(` or `)`.\n" "2. PubMed Central ID, cite like `@pmcid:PMC4497619`.\n" "3. PubMed ID, cite like `@pmid:26158728`.\n" "4. _arXiv_ ID, cite like `@arxiv:1508.06576v2`.\n" "5. ISBN (International Standard Book Number), cite like `@isbn:9781339919881`.\n" "6. URL / webpage, cite like `@url:https://nyti.ms/1QUgAt1`.\n" " URL citations can be helpful if the above methods return incorrect metadata.\n" " For example, `@doi:10.1038/ng.3834` [incorrectly handles](https://github.com/manubot/manubot/issues/158) the consortium name resulting in a blank author, while `@url:https://doi.org/10.1038/ng.3834` succeeds.\n" " Similarly, `@url:https://doi.org/10.1101/142760` is a [workaround](https://github.com/manubot/manubot/issues/16) to set the journal name of bioRxiv preprints to _bioRxiv_.\n" "7. Wikidata Items, cite like `@wikidata:Q50051684`.\n" " Note that anyone can edit or add records on [Wikidata](https://www.wikidata.org), so users are encouraged to contribute metadata for hard-to-cite works to Wikidata as an alternative to using a `raw` citation.\n" "8. For references that do not have any of the persistent identifiers above, use a raw citation like `@raw:old-manuscript`.\n" " Metadata for raw citations must be provided manually.\n\n" "Cite multiple items at once like:\n\n" "```md\n" "Here is a sentence with several citations [@doi:10.15363/thinklab.4; @pmid:26158728; @arxiv:1508.06576; @isbn:9780394603988].\n" "```\n\n" "More information at https://github.com/manubot/rootstock/blob/master/USAGE.md#citations\n\n" "## Invalid citekeys\n\n" "Citekeys in this section would be nice to support, but notice that they do not completely match the regex:\n\n" "Citekey with parentheses @doi:10.1016/S0022-2836(05)80360-2\n" "Citekey with closing slash @https://www.google.com/\n" "Citekey with equal sign @https://openreview.net/forum?id=HkwoSDPgg\n\n" "See https://github.com/jgm/pandoc/issues/6026 for discussion on a more flexible markdown syntax for citation keys.\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