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

/
/
gm

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"(?x) # invoke extended (aka free-spacing) mode\n" r"^ # match beginning of the string\n" r"[^\"\n]* # match zero or more chars other than line terminators and double-quotes\n" r"\" # match a double-quote\n" r"[^\"\n]* # match zero or more chars other than line terminators and double-quotes\n" r"(?<! # begin a negative lookbehind\n" r" \ # match a space\n" r" | # or\n" r" \\n # match a backslash followed by n\n" r") # end negative lookbehind\n" r"\" # match a double-quote\n" r"\n # match a newline\n" r"\ * # match zero or more spaces\n" r"\" # match double-quote\n" r"[^ \"\n] # match a character other than a space, double-quote or newline\n" r"[^\"\n]* # match zero or more chars other than line terminators and double-quotes\n" r"\" # match a double-quote\n" r"\n? # optionally match a newline\n" r"$ # match end of string") test_str = ("a c\"d1 %\"\n" " \"&g i\"\n\n" "\"9\"\n" "\"&\"\n\n" "d a\"fe \"\n" " \"3h j\"\n\n" "a c\"d1 \\n\"\n" " \"&g i\"\n\n" "a\"de f%x\"\n" " \" &12 \"\n\n" "#3 does not match due to space preceding second double-quote\n" "#4 does not match due to a backslash followed by n preceding second double-quote\n" "#5 does not match due to backslash followed by n following third double-quote\n" "#5 does not match due to space following third double-quote\n") matches = re.finditer(regex, test_str, re.MULTILINE) 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