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

/
/
gmi

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"[-\[,:.\/]?\b(?:1\d{3}|200[0123]|\d0)(?:'?s)?\b[-\],:.\/]?" test_str = ("I need it to catch a date between 1000 and 2003 in these forms:\n" "1975\n" "1970s\n" "1970's\n" "1970S\n" "1970'S\n" "70s\n" "70's\n" "70S\n" "70'S\n\n" "I also need it to catch certain characters on either side of the date, including\n" "dashes\n" "-1973-\n" "brackets\n" "[1973]\n" "commas\n" ",1973,\n" "colons\n" ":1973:\n" "periods\n" ".1973.\n" "slashes\n" "/1973/\n\n" " - some on both sides, some on only one.\n" "/1973\n" "or\n" "1973/\n\n" "My problem is that the expression is catching other characers on either side of the date as well - +1975 gets through, for instance, as does 1970s& - letters and numbers on either side do not get through, however. I'm confused.\n\n" "I think I might need some sort of limit on either side before I can state the exceptions, I'm not sure what that would look like - some kind of look back? Any help would be appreciated.") matches = re.finditer(regex, test_str, re.MULTILINE | re.IGNORECASE) 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