Regular Expressions 101

Save & Manage Regex

  • Current Version: 1
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
Sponsors
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"^(?![^?\n]*\?).*good\s+answer", flags=re.MULTILINE) test_str = ("Here are the strings I want to detect:\n" "--------------------------------------\n" "That a very good answer!\n" "(Other than that, this is a really good answer and I've upvoted it.)\n" "good answer dvdf!\n" "dsds good answer cfds\n" "It is a good answer, but I feel it played into the OP's hands really. You said what they wanted to hear - that they shouldn't freely share the information because it is like a child cheating on their homework. It is contrary to the spirit of this site, and I'm not sure that charging a colleague money to learn something work-based from you won't get the OP into trouble with their employer. Imagine if a doctor asked to confer with a fellow doctor in order to help a patient, and they charged each other for the information they shared. They'd be dismissed.\n\n" "Here are the one I don't want to detect\n" "-----------------------------------------\n" "Thanks for this good answer! (I upvoted it) However, I still don't understand why I shouldn't mention that I believe whatever? What's the problem with that...\n" "cxvd good answer? zedfs\n" "ezdds? good answer dsf dsf\n" "sdsd? dsfdsf? good answer!\n" "Hi, the question is \"How to tell blabla when X is my good friend\", would you mind be a little more detail about how OP should do that when OP still want to be friend with both parties? Also, please take some time to read \"How do I write a good answer\n" "As a side note, here is a link to \"How do I write a good answer?\n" "Hi, this sound like a good answer to me, I just have one question though: Where you in a similar situation before where you successfully used this technic? In here it's better to back-up your answer with personal experience (here is a guide to How to write a good answer if you need it)") 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