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"\b6(?:011|5[0-9]{2})[ -]([0-9]{4}[ -]){2}([0-9]{4})\b|\b6(?:011|5[0-9]{2})(?:[0-9]{12})?$\b" test_str = ("Discover\n\n" "Requirements: Discover cards start with the number 6011 or 65 and have 16 digits. \n\n" "Pattern Parts:\n" "Starts with number 6011 or 65, has 16 length, and has space or dash:\n" "1) \\b6(?:011|5[0-9]{2})[ -]([0-9]{4}[ -]){2}([0-9]{4})\\b\n\n" "Starts with number 6011 or 65, has 16 length, and has no space or dash:\n" "2) \\b6(?:011|5[0-9]{2})(?:[0-9]{12})?$\\b\n\n" "Combining 1-2 to form one pattern:\n" "\\b6(?:011|5[0-9]{2})[ -]([0-9]{4}[ -]){2}([0-9]{4})\\b|\\b6(?:011|5[0-9]{2})(?:[0-9]{12})?$\\b\n\n\n" "Test Cases:\n" "Positive (Should fire):\n" "16 length, no space, start with 6011 6011123412341234\n" "16 length, dashes, start with 6011 6011-1234-1234-1234\n" "16 length, spaces, start with 6011 6011 1234-1234-1234\n\n" "16 length, no space, start with 65 6521123412341234\n" "16 length, dashes, start with 65 6521-1234-1234-1234\n" "16 length, spaces, start with 65 6521 1234 1234 1234\n\n" "Embedded in sentence with space:\n" "16 length, no space, start with 6011 Here is the cc: 6011123412341234\n" "16 length, dashes, start with 6011 Here is the cc: 6011-1234-1234-1234\n" "16 length, spaces, start with 6011 Here is the cc: 6011 1234-1234-1234\n\n" "16 length, no space, start with 65 Here is the cc: 6521123412341234\n" "16 length, dashes, start with 65 Here is the cc: 6521-1234-1234-1234\n" "16 length, spaces, start with 65 Here is the cc: 6523 1234-1234-1234\n\n" "16 length, no space, start with 6011 Credit Card#:6011123412341234\n" "16 length, dashes, start with 6011 Credit Card#:6011-1234-1234-1234\n" "16 length, spaces, start with 6011 Credit Card#:6011 1234-1234-1234\n\n" "16 length, no space, start with 65 Credit Card#:6521123412341234\n" "16 length, dashes, start with 65 Credit Card#:6521-1234-1234-1234\n" "16 length, spaces, start with 65 Credit Card#:6523 1234-1234-1234\n\n" "Negative (Should Not Fire):\n" "16 length, no space, not start with 6012 6012123412341234\n" "16 length, dashes, not start with 6012 6012-1234-1234-1234\n" "16 length, spaces, not start with 6012 6012 1234 1234 1234\n\n" "16 length, no space, not start with 66 6612123412341234\n" "16 length, dashes, not start with 66 6612-1234-1234-1234\n" "16 length, spaces, not start with 66 6612-1234-1234-1234\n\n" "16 length, no space, start with 65, embedded Credit Card Number6521123412341234\n" "16 length, dashes, start with 6011, malformed 601-11234-1234-1234\n\n" "16 length num matching pattern but embedded User ID: 0000006011123412341234000000") 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