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
No Match

/
/
g

Test String

Code Generator

Language

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r" *(?:.*\S.*\n)+\n? *: +(?:.|\n)+?(?:\n{2,}(?=\S)(?! *: +)(?! *(?:\S.*\n)+?\n? *: +)|$)" test_str = ("=== Single <dt> and <dd>\n\n" "GitHub\n" ": a site where over 73 million developers shape the future of software, together\n\n" "=== Multiple <dt>-<dd> group\n\n" "Firefox\n" ": a free, open source, cross-platform, graphical web browser developed by the Mozilla Corporation and hundreds of volunteers\n\n" "MDN\n" ": provides information about Open Web technologies including HTML, CSS, and APIs for both Web sites and progressive web apps\n\n" "=== Single <dt> with multiple <dd>s\n\n" "Apple\n" " : an American multinational technology company that specializes in consumer electronics, computer software and online services.\n" " : an edible fruit produced by an apple tree\n\n" "=== Multiple <dt>s\n\n" "Windows\n" "Microsoft Windows\n" "Win\n" ": a group of several proprietary graphical operating system families, all of which are developed and marketed by Microsoft\n\n" "=== separated by blank lines\n\n" "Solaris\n\n" ": a 1961 science fiction novel by Polish writer Stanisław Lem\n\n\n\n" ": a proprietary Unix operating system originally developed by Sun Microsystems\n\n" "=== <dd>s with inline breaks\n\n" "Oracle\n" ": an American multinational computer technology\n" "corporation headquartered in Austin, Texas\n\n" ": the priest or priestess uttering the prediction,\n" "may also refer to the site of the oracle\n\n" "===\n\n" "😂\n" ": 😂 face with tears of joy\n\n" "===\n\n" "Term 1\n\n" ": This is a definition with two paragraphs. Lorem ipsum \n" " dolor sit amet, consectetuer adipiscing elit. Aliquam \n" " hendrerit mi posuere lectus.\n\n" " Vestibulum enim wisi, viverra nec, fringilla in, laoreet\n" " vitae, risus.\n\n" ": Second definition for term 1, also wrapped in a paragraph\n" " because of the blank line preceding it.\n\n" "Term 2\n\n" ": This definition has a code block, a blockquote and a list.\n\n" " code block.\n\n" " > block quote\n" " > on two lines.\n\n" " 1. first list item\n" " 2. second list item") matches = re.finditer(regex, test_str) for matchNum, match in enumerate(matches, start=1): print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group())) for groupNum in range(0, len(match.groups())): groupNum = groupNum + 1 print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum))) # Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

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