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

/
/
gmis

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"(?<!```html\s*)(<link href=.*?)(?=^\s*$)" test_str = ("\n" "# PATTERNS\n\n" "## Style Blocks (2 patterns)\n" "- ***Matches:***\n" " - All `<style> any code here </style> blocks that aren't preceded by ```css + any amount of optional whitespace\n\n" ">> NOTES FOR THE FOLLOWING PATTERN: \n" " • This requires the `regex` library, not Python's built-in-crap\n" " • This requires the `Single Line` (regex101) or `regex.DOTALL` (Python regex) flag\n\n" "### Pattern: Old version (would have replaced all punctuation with `punctuation` from the string library)\n" " (?<!```css\\s*)(\\<style\\>[\\sa-z0-9\\-\\.\\[\\{\\]\\}:;#]+\\<\\/style\\>)\n\n" ">> NOTES FOR THE FOLLOWING PATTERN: \n" " • This requires the `regex` library, not Python's built-in-crap\n" " • This requires the `Single Line` (regex101) or `regex.DOTALL` (Python regex) flag\n\n" "### Pattern: Newest version (much better)\n" " (?<!```css\\s*)(<style>.*?<\\/style>)\n\n" "## This does the same thing but for `<!DOCTYPE html> any code here </html>`\n\n" ">> NOTES FOR THE FOLLOWING PATTERN: \n" " • This requires the `regex` library, not Python's built-in-crap\n" " • This requires the `Single Line` (regex101) or `regex.DOTALL` (Python regex) flag\n\n" "### Pattern:\n" " (?<!```html\\s*)(<!DOCTYPE html>.*?<\\/html>)\n\n" "## This matches all blocks of code containing `<link href=>` up to, but not including, an empty line\n\n" ">> NOTES FOR THE FOLLOWING PATTERN: \n" " • This requires the `regex` library, not Python's built-in-crap\n" " • This requires the `Single Line` (regex101) or `regex.DOTALL` (Python regex) flag\n\n" "### Pattern:\n" " (?<!```html\\s*)(<link href=.*?)(?=^\\s*$)\n\n" "<br>\n\n" "(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)(><)\n\n" "<br>\n\n" "# TEST TEXT\n\n" "<br>\n\n" "<style>\n" " .list-group-mine .list-group-item {\n" " background-color: black;\n" " color: white;\n" " border-top: 1px solid #0091b5;\n" " border-left-color: #fff;\n" " border-right-color: #fff;\n" " }\n" " .list-group-mine .list-group-item:hover {\n" " background-color: red;\n" " }\n" "</style>\n\n\n" "```css\n" "<style>\n" " .list-group-mine .list-group-item {\n" " background-color: black;\n" " color: white;\n" " border-top: 1px solid #0091b5;\n" " border-left-color: #fff;\n" " border-right-color: #fff;\n" " }\n" " .list-group-mine .list-group-item:hover {\n" " background-color: red;\n" " }\n" "</style>\n" "```\n\n" "<link href=\"https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css\" rel=\"stylesheet\" integrity=\"sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u\" crossorigin=\"anonymous\">\n" "<div class=\"list-group list-group-mine\">\n" " <a class=\"list-group-item\" href=\"https://bit.ly/3SICqay\"><strong>Link to the SO Post</strong></a>\n" " <a class=\"list-group-item\" href=\"/path\"><strong>Item 2</strong></a>\n" " <a class=\"list-group-item\" href=\"/path\"><strong>Item 3</strong></a>\n" "</div>\n\n" "<br>\n\n" "##### Before Bootstrap\n" "<!DOCTYPE html>\n\n" "<html lang=\"en\">\n" " <head>\n" " <title>TABLE</title>\n" " </head>\n" " <body>\n" " <table>\n" " <thead>\n" " <tr>\n" " <th>Name</th>\n" " <th>Number</th>\n" " </tr>\n" " </thead>\n" " <tbody>\n" " <tr>\n" " <td>Malachi</td>\n" " <td>1-555-343-9867</td>\n" " </tr>\n" " <tr>\n" " <td>Steve</td>\n" " <td>1-555-734-8857</td>\n" " </tr>\n" " </tbody>\n" " </table>\n" " </body>\n" "</html>\n\n\n" "</br>\n\n" "<code style=\"color: #f51686; font-weight: bold; font-size: 16pt;\"> The HTML </code>\n\n" "```html\n" " <!DOCTYPE html>\n" " <html lang=\"en\">\n" " <head>\n" " <meta charset=\"UTF-8\" />\n" " <meta http-equiv=\"X-UA-Compatible\" content=\"IE=edge\" />\n" " <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\" />\n" " <title>CSS Images</title>\n" " <link rel=\"stylesheet\" href=\"css/style.css\" />\n" " </head>\n\n" " <body>\n" " <div class=\"container\">\n" " <section class=\"hero\">\n" " <figure class=\"profile-pic-figure\">\n" " <img\n" " src=\"img/profile-800x800.png\"\n" " alt=\"profile\"\n" " width=\"800\"\n" " height=\"800\"\n" " title=\"Profile Pic\"\n" " />\n" " <figcaption class=\"offscreen\">Pookie Scrumptious</figcaption>\n" " </figure>\n" " <h1 class=\"h1\">\n" " <span class=\"nowrap\">\n" " Hello 👋\n" " </span>\n" " <span class=\"nowrap\">\n" " I'm Pookie\n" " </span>\n" " </h1>\n" " </section>\n" " </div>\n" " </body>\n" " </html>\n" "```\n\n" "<br>\n\n" "<code style=\"color: #f51686; font-weight: bold; font-size: 16pt;\"> The CSS</code>\n") matches = re.finditer(regex, test_str, re.MULTILINE | re.IGNORECASE | re.DOTALL) 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