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"^(.+)$(?=[\s\S]*^(\1)$[\s\S]*)") test_str = ("\n\n" "An HTML attachment was scrubbed...\n" "URL: https://list.something.edu/mailman/attachments/200908002/7452/attachment.html\n" "From SomeAddress at SomeDomain.org SomeDate\n" "From: SomeonesEmail at SomeDomain.org (FirstName LastName)\n" "Date: [the date]\n" "Subject: [ListservName] SomeSubject\n" "In-Reply-To: <SomeIDnumber>\n" "References: <%SomeEmailAddress>\n" " <SomeIDnumber>\n" "Message-ID: <SomeIDnumber>\n\n" "Hey there, Everyone,\n\n" "I completely disagree with this. It's crap!\n\n" "Sincerely,\n" "SomePerson\n\n\n\n" "On SomeDate, Someone wrote:\n" "From: SomeonesEmail at SomeDomain.org (FirstName LastName)\n" "Date: [the date]\n" "Subject: [ListservName] SomeSubject\n" "In-Reply-To: <SomeIDnumber>\n" "References: <%SomeEmailAddress>\n" " <SomeIDnumber>\n" "Message-ID: <SomeIDnumber>\n\n" "Hey PersonA,\n\n" "This is my advice. It is really good advice. I hope you take it since I think it's pertinent.\n\n" "Sincerely,\n" "PersonZ\n\n\n\n\n" "An HTML attachment was scrubbed...\n" "URL: https://list.something.edu/mailman/attachments/200908002/7452/attachment.html\n" "From SomeAdress at SomeDomain.org SomeDate\n" "From: SomeonesEmail at SomeDomain.org (FirstName LastName)\n" "Date: [the date]\n" "Subject: [ListservName] SomeSubject\n" "In-Reply-To: <SomeIDnumber>\n" "References: <%SomeEmailAddress>\n" " <SomeIDnumber>\n" "Message-ID: <SomeIDnumber>\n\n" "Good Afternoon, PersonA,\n\n" "But have you considered this aspect? It changes everything, so this is my advice. It is even better advice! \n\n" "Sincerely,\n" "PersonB\n\n\n\n" "On SomeDate, PersonZ wrote:\n\n" "Hey PersonA,\n\n" "This is my advice. It\n" "is really\n" "good advice. I hope you take it since I\n" "think it's pertinent.\n\n" "Sincerely,\n" "PersonZ\n\n\n\n" "From SomeAddress at SomeDomain.org SomeDate \n" "From: SomeonesEmail at SomeDomain.org (FirstName LastName)\n" "Date: [the date]\n" "Subject: [ListservName] SomeSubject\n" "In-Reply-To: <SomeIDnumber>\n" "References: <%SomeEmailAddress>\n" " <SomeIDnumber>\n" "Message-ID: <SomeIDnumber>\n\n" "Thank you all for your feedback on this issue. You've given me a lot to\n" "consider. Cheers.\n\n\n\n" "[And so on.]\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