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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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"(?<code1>id=\"question-summary-)(?<code2>\d+)" test_str = ("<div class=\"question-summary\" id=\"question-summary-80407\">\n" " <div class=\"statscontainer\">\n" " <div class=\"statsarrow\"></div>\n" " <div class=\"stats\">\n" " <div class=\"vote\">\n" " <div class=\"votes\">\n" " <span class=\"vote-count-post \"><strong>2</strong></span>\n" " <div class=\"viewcount\">votes</div>\n" " </div>\n" " </div>\n" " <div class=\"status answered\">\n" " <strong>1</strong>answer\n" " </div>\n" " </div>\n\n\n\n" " <div class=\"views \" title=\"60 views\">\n" " 60 views\n" " </div>\n" " </div>\n" " <div class=\"summary\">\n" " <h3><a href=\"/questions/80407/about-power-supply-of-opertional-amplifier\" class=\"question-hyperlink\">about power supply of opertional amplifier</a></h3>\n" " <div class=\"excerpt\">\n" " I am constructing an operational amplifier as shown in the following figure. I use a batter as supplier for the OP Amp and set it up as a non-inverting amp circuit. I saw that the output was clipped ...\n" " </div>\n\n" " <div class=\"tags t-op-amp\">\n" " <a href=\"/questions/tagged/op-amp\" class=\"post-tag\" title=\"show questions tagged 'op-amp'\" rel=\"tag\">op-amp</a>\n\n" " </div>\n" " <div class=\"started fr\">\n\n\n" " <div class=\"user-info \">\n" " <div class=\"user-action-time\">\n\n\n" " asked <span title=\"2013-08-27 21:49:14Z\" class=\"relativetime\">11 hours ago</span>\n" " </div>\n" " <div class=\"user-gravatar32\">\n" " <a href=\"/users/17060/user1285419\"><div class=\"\"><img src=\"https://www.gravatar.com/avatar/08ee68b20a4eceff26f7eee99b708c08?s=32&d=identicon&r=PG\" alt=\"\" width=\"32\" height=\"32\"></div></a>\n" " </div>\n" " <div class=\"user-details\">\n" " <a href=\"/users/17060/user1285419\">user1285419</a><br>\n" " <span class=\"reputation-score\" title=\"reputation score\" dir=\"ltr\">165</span><span title=\"5 bronze badges\"><span class=\"badge3\"></span><span class=\"badgecount\">5</span></span>\n" " </div>\n" " </div>\n\n" " </div>\n" " </div>\n" " </div>\n\n" " <div class=\"question-summary\" id=\"question-summary-80405\">\n" " <div class=\"statscontainer\">\n" " <div class=\"statsarrow\"></div>\n" " <div class=\"stats\">\n" " <div class=\"vote\">\n" " <div class=\"votes\">\n" " <span class=\"vote-count-post \"><strong>4</strong></span>\n" " <div class=\"viewcount\">votes</div>\n" " </div>\n" " </div>\n" " <div class=\"status answered-accepted\">\n" " <strong>2</strong>answers\n" " </div>\n" " </div>\n\n\n\n" " <div class=\"views \" title=\"64 views\">\n" " 64 views\n" " </div>\n" " </div>\n" " <div class=\"summary\">\n" " <h3><a href=\"/questions/80405/5v-regulator-power-dissipation\" class=\"question-hyperlink\">5V Regulator Power Dissipation</a></h3>\n" " <div class=\"excerpt\">\n" " I am using a 5V regulator (LP2950) from ON Semiconductor. I am using this for USB power and I'm feeding in 9V from an adapter. USB requires maximum of 500mA right? So the maximum power dissipation in ...\n" " </div>\n\n" " <div class=\"tags t-voltage-regulator t-surface-mount t-heatsink t-5v t-power-dissipation\">\n" " <a href=\"/questions/tagged/voltage-regulator\" class=\"post-tag\" title=\"show questions tagged 'voltage-regulator'\" rel=\"tag\">voltage-regulator</a> <a href=\"/questions/tagged/surface-mount\" class=\"post-tag\" title=\"show questions tagged 'surface-mount'\" rel=\"tag\">surface-mount</a> <a href=\"/questions/tagged/heatsink\" class=\"post-tag\" title=\"show questions tagged 'heatsink'\" rel=\"tag\">heatsink</a> <a href=\"/questions/tagged/5v\" class=\"post-tag\" title=\"show questions tagged '5v'\" rel=\"tag\">5v</a> <a href=\"/questions/tagged/power-dissipation\" class=\"post-tag\" title=\"show questions tagged 'power-dissipation'\" rel=\"tag\">power-dissipation</a>\n\n" " </div>\n" " <div class=\"started fr\">\n\n\n" " <div class=\"user-info \">\n" " <div class=\"user-action-time\">\n\n\n" " asked <span title=\"2013-08-27 21:39:31Z\" class=\"relativetime\">11 hours ago</span>\n" " </div>\n" " <div class=\"user-gravatar32\">\n" " <a href=\"/users/10082/david-norman\"><div class=\"\"><img src=\"https://www.gravatar.com/avatar/8b073417e471077280b3fc5ff2eaf1f7?s=32&d=identicon&r=PG\" alt=\"\" width=\"32\" height=\"32\"></div></a>\n" " </div>\n" " <div class=\"user-details\">\n" " <a href=\"/users/10082/david-norman\">David Norman</a><br>\n" " <span class=\"reputation-score\" title=\"reputation score\" dir=\"ltr\">322</span><span title=\"3 silver badges\"><span class=\"badge2\"></span><span class=\"badgecount\">3</span></span><span title=\"10 bronze badges\"><span class=\"badge3\"></span><span class=\"badgecount\">10</span></span>\n" " </div>\n" " </div>\n\n" " </div>\n" " </div>\n" " </div>") 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