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"(?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 = 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