Regular Expressions 101

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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

r"
"
g

Test String

Substitution

Processing...

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"(\n|;|^)\"([^\";\n]*?)\"([^\";\n]+?)\"([^\";\n]*?)\"(\n|;|$)" test_str = ("A stable and simple RegEx, which escapes double-quotes (\") in a CSV file.\n\n" "## Tests ##\n" "\"Great thing?!*\";\"I love RegEx!\";\"And especially \"regex101.com\"!\";\"Just amazing...\"\n" "\"Something090324*?!*\";\"Somethi\"ng090\"324*?!*\";\"Something090324*?!*\";\"Something090324*?!*\"\n" "Ignore\"THIS\"ItIsNotARealQuote?!*;\"This\"is\"real!\";HereIsNoQuoteSymbolAtAll;This\"IsOnlyOneQuoteSymbol\n\n" "CSV: Escape double-quotes (\") in quoted \n\n" "## Issues ##\n" "- Does not support embedded line breaks, but you can easily modify it to support them. Note that they are currently forbitten to be more stable.\n" "- Does only allow \" for quoting. (Replace it in the whole RegEx to change this)\n" "- Only works with ; as a separator. (Replace it in the whole RegEx to change this)\n" "- Does not allow separator character inside of quotes string. Look at the following example:\n" "\"Example \"string\"\";\"works\"\n" "\"Example \"string\";\";\"fails\"\n" "- Get's problems when the issue happens \"too often\", which means it shows up in cells which are directly side-by-side. You may work around this issue by running it multiple times:\n" "\"run 1 time \";\"a string with a \"small\" issue\";\"and \"another\" one\"\n" "\"run 2 times\";\"a string with a \"\"small\"\" issue\";\"and \"another\" one\"\n" "- It only works with quoted strings (no single \" are escaped; only double ones)\n\n" "## Changelog ##\n" "v1.0 - 2016-01-25\n" "- released\n\n" "Author: rugk <rugk@posteo.de>") subst = "\\1\"\\2\"\"\\3\"\"\\4\"\\5" # You can manually specify the number of replacements by changing the 4th argument result = re.sub(regex, subst, test_str, 0) if result: print (result) # 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