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

/
/
g

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"(?m)^(?: +|\t+)\+ *(?:VAR|CONST) *\w+ *=.*(?:\R^(?> +|\t+)[^+\s].*)*" test_str = (" + VAR name1 = var indented by two spaces and the first nonspace character is '+'\n" " + VAR name2 = var indented by 2x2 spaces\n\n" " + VAR name3 = var indented by one \\t\n" " + VAR name4 = the next line with \"name5\" is not valid. missing the = character, should not be matched\n" " + VAR name5\n" " + CONST name6 = the type could be VAR or CONST\n\n" " + VAR multi1 = multiline value where the continuation lines\n" " are indented (starts with two spaces or one tab) and NOT followed by the '+'\n\n" " + VAR multi1 = multiline value\n" " indented\n\n" " + VAR multi1 = multiline value\n" " indented ok too\n\n\n" " + VAR single = this is single line\n" " + because this line even if it is indented, the first nonspace character is '+'\n\n" " + VAR multi2 = multiline\n" " could be\n" " indented\n" " any way\n" " and any number of times\n" " until the first non-indented line\n\n" "the following should NOT match\n\n" "+ VAR some = sould not be matched, because the line isn't indented\n" " + VAR some = sould not be matched, because the line isn't indented at least with TWO spaces or one tab\n" " + SOME name = value not matched because the SOME isn't VAR or CONST") matches = re.finditer(regex, test_str) 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