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

/
/
gmx

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""" # Leap Years are any year that can be evenly divided by 4 # (such as 2012, 2016, etc) # • except if it can be evenly divided by 100 # then it isn't (such as 2100, 2200, etc) # • except if it can be evenly divided by 400, # then it is (such as 2000, 2400) # https://www.mathsisfun.com/leap-years.html # ------------------------------------------------- # verify date dd/mm/yyyy; possible separators: -.,/ # valid year range: 0000-9999 ^ # start anchor # precheck xx-xx-xxxx,... add new separators here (?=\d{2}([-.,\/])\d{2}\1\d{4}$) (?: # day-check: non caturing group # days 01-28 0[1-9]|1\d|[2][0-8]| # february 29d check for leap year: all 4y / 00 years: only each 400 # 0400,0800,1200,1600,2000,... 29 (?!.02. # not if feb: if not ... (?! # 00 years: exclude !0 %400 years (?!(?:[02468][1-35-79]|[13579][0-13-57-9])00) # 00,04,08,12,... \d{2}(?:[02468][048]|[13579][26]) ) )| # d30 negative lookahead: february cannot have 30 days 30(?!.02)| # d31 positive lookahead: month up to 31 days 31(?=.(?:0[13578]|10|12)) ) # eof day-check # month 01-12 .(?:0[1-9]|1[012]) # year 0000-9999 .\d{4} $ # end anchor """ test_str = ("29/02/0000\n" "29/02/0100\n" "29/02/0200\n" "29/02/0300\n" "29/02/0400\n" "29/02/0500\n" "29/02/0600\n" "29/02/0700\n" "29/02/0800\n" "29/02/0900\n" "29/02/1000\n" "29/02/1100\n" "29/02/1200\n" "29/02/1300\n" "29/02/1400\n" "29/02/1500\n" "29/02/1600\n" "29/02/1700\n" "29/02/1800\n" "29/02/1900\n" "29/02/2000\n" "29/02/2100\n" "29/02/2200\n" "29/02/2300\n" "29/02/2400\n" "29/02/2500") matches = re.finditer(regex, test_str, re.MULTILINE | re.VERBOSE) 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