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

Generated Code

import re regex = re.compile(r""" (?P<content>.*?) # Content up to next tag (?P<markup> # Entire tag <!\[CDATA\[(?P<cdata>.+?)]]>| # <![CDATA[ ... ]]> <!--(?P<comment>.+?)-->| # <!-- Comment --> </\s*(?P<close_tag>\w+)\s*>| # </tag> <(?P<tag>\w+) # <tag ... (?P<attributes> (?P<attribute>\s+ # <snip>: Use this part to get the attributes out of 'attributes' group. (?P<attribute_name>\w+) (?:\s*=\s* (?P<attribute_value> [\w:/.\-]+| # Unquoted (?=(?P<_v> # Quoted (?P<_q>['\"]).*?(?<!\\)(?P=_q))) (?P=_v) ))? # </snip> )* )\s* (?P<is_self_closing>/?) # Self-closing indicator >) # End of tag """, flags=re.DOTALL | re.VERBOSE) test_str = ("In this case, $url will indeed contain http://example.com/whatever.jpg. But what happens when you start getting HTML like this:\n\n" "<img src='http://example.com/whatever.jpg'>\n" "or\n\n" "<img src=http://example.com/whatever.jpg>\n" "or\n\n" "<img border=0 src=\"http://example.com/whatever.jpg\">\n" "or\n\n" "<img border src=\"http://example.com/whatever.jpg\">\n" "or\n\n" "<img\n" " src=\"http://example.com/whatever.jpg\">\n" "or you start getting false positives from\n\n" "<!-- // commented out\n" "<img src=\"http://example.com/outdated.png\">\n" "-->\n\n" "<script><![CDATA[ This is <b>not</b> parsed ]]></script>\n\n" "<asd ASD=asd>\n\n" "<!-- // commented out <img src=\"http://example.com/outdated.png\"> -->\n\n" "No quotes:\n" "<iframe src=test.html target=xyz></ iframe >\n" "Self-closing tag:\n" "<a href=test.html target=xyz/>\n" "Self closing tag with a space before closure:\n" "<a href=test.html target=xyz />\n" "Double quotes:\n" "<a href=\"test.html\" target=\"xyz\">\n" "Single quotes:\n" "<a href='test.html' target='xyz'>\n" "Escaping double quotes:\n" "<a href=\"test.html?val=1\" title=\"\\\"No rules exist\\\" Andre Breton's quote\">\n" "Escaping single quotes (also with spaces between equals signs):\n" "<a href = \"test.html?val=1\" title = 'Charlie\\'s Angels'>\n" "Tag without closure (ignored):\n" "<a href = \"test.html?val=1\" title='Charlie\\'s Angels'\n" "Tag without opening (ignored):\n" "a href = \"test.html?val=1\" title=\"Charlie\\\"s Angels\">\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