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

r"
"
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"(?:^|\b(?<!\.))(?:1?\d?\d|2[0-4]\d|25[0-5])(?:\.(?:1?\d?\d|2[0-4]\d|25[0-5])){3}(?=$|[^\w.])" test_str = ("My input string & constraints are as follows :\n\n" " IPv4 Range : 0.0.0.0 to 255.255.255.255 55.123.99.988 256.1.1.1\n" " IPv4 address may / may not be present in the string\n" " Valid Examples : this is an ip & this is an ip 200.100.2.32\n" " String may start with IPv4 address\n" " Valid Examples :\n" "200.100.2.32 is an ip | Output : ['200.100.2.32']\n" " Invalid Examples :\n" "200.100.2.32is an ip | Output : []\n" " String may end with IPv4 address\n" " Valid Examples : the ip is 200.100.2.32\n" "Output : ['200.100.2.32']\n" " Invalid Examples : the ip is200.100.2.32\n" "Output : []\n" " String may contain an IPv4 address in the middle, and if it does - there will a space before and after the IPv4 address.\n" " Valid Examples : the ip is 200.100.2.32 and it is ipv4 | Output : ['200.100.2.32']\n" " Valid Examples : the ip is 200.100.2.32and it is ipv4 | Output : []\n" " Multiple IPs may be present in a single string\n" " Valid Examples : 200.100.2.32 100.50.1.16 | Output : ['200.100.2.32', '100.50.1.16']\n" " Invalid Examples : 200.100.2.32.100.50.1.16 | Output : []\n" "10.151.0.0,8.8.8.8,127.0.0.1,10.51.0.0,10.151.1.0") 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