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"\b(?<!\d.)(3[47]\d{2}([ -]?)(?!(\d)\3{5}|123456|234567|345678|424242|545454)\d{6}\2(?!(\d)\4{4})\d{5}|((4\d|5[1-5]|65)\d{2}|6011)([ -]?)(?!(\d)\8{3}|4242|5454|1234|3456|5678|2345|4567)\d{4}\7(?!(\d)\9{3})\d{4}\7\d{4})(\b|\s)(?!.\d\d)" test_str = ("ALL strings in the first section should match\n" "some 4270446050075048\n" "4270-4460-5007-5048\n" "this:4270 4460 5007 5048.\n" "4270 4460 5007 5048 4/20\n" "4270 4460 5007 5048 what\n" "4270 4460 5007 5048\n" "4270 4460 5007 5048 12/20 \n" "5105105105105100\n" "5200828282828210\n\n" "--- (the following should not match - test numbers)\n" "5454545454545454\n" "4123456789012345\n" "4242424242424242\n" "42704460500750a8\n" "4111111111111111\n" "5111111111111111\n" "5555555555555555\n" "3333333333333333\n" "3111111111111111\n\n" "--- (the following should NOT match)\n" "4270 4460 5007 5048 1234\n" "4270\n" "4270 4460 5007 504\n" "42811293test123\n" "427044605007504812345083 5095 5179 5157 5219 5187 5095 <--- FALSE POSITIVE (contains valid CC but has lots of exra digits)\n" "this:4270 4460 5007 50482\n" "4270 4460 5007 5048 123\n" "4270 4460 5007 5048 1234\n\n" "Known False positive (test number):\n" "5535 3545 5455 4444\n") 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