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"K'(?|(?P<name1>81)\d+|(61)\d+|(64)\d+|(1)\d+|(44)\d+|(86)\d+|(678)\d+|(41)\d+|(49)\d+|(33)\d+|(685)\d+|(\d{1,3})\d+)" test_str = ("K'8134567\n" "K'81345678\n" "K'6134516789\n" "K'61345678\n" "K'643456\n" "K'646345678\n" "K'1234567890\n" "K'12345678901\n" "K'1454567890 <<<--- want 145 returned and not 1 \n" "K'13345678901 <<<--- want 133 returned and not 1 \n" "K'3214567890123\n" "K'32134567890123\n" "K'3654567890123\n" "K'8934567890123\n" "K'6554567890123\n\n\n" "I am interested in the digits after K'\n" "I am looking to do this using regex but not sure if it can be done. What I want is:\n" "if the number starts with 81 return 81 \n" "if the number starts with 61 return 61 \n" "...\n" "if the number starts with something i am not interested in return other(or its first digits of 1-3)\n\n" "The above criteria works:\n\n" "but what I also want is:\n" "if the fist digit is 1 then return 1 BUT \n" "if the fist digit is 1 and the 2nd and 3rd digit are 45 return 145 and don't return just 1 \n" "if the fist digit is 1 and the 2nd and 3rd digit are 33 return 133 and don't return just 1\n\n" "I presume I have to put something inside this part of the regex |(1)\\d+|\n\n" "Questions:\n" "Does regex sort the data first?\n" "Is the order of the regex search important to how it is implemented? i deally I do not want this. \n\n\n\n\n\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