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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"^(((([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]))|((([a-zA-Z]|[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)+([A-Za-z|[A-Za-z][A-Za-z0-9\‌​-]*[A-Za-z0-9])))$", flags=re.MULTILINE) test_str = ("foo\n" "foo.bar\n" "www.foo.bar\n\n" ".foo\n" "foo.\n" "foo.com.\n" ".com.bar\n\n" "foo-bar.com\n" "foo-bar.com-eu\n" "foo.bar.com\n\n" "0.foo.bar\n" "foo.1.bar\n" "foo.bar.2\n" ".1.bar.com\n\n" "foo.bar1.com\n" "foo.2bar.com\n" "foo.bar3.com\n" "foo.bar.4com\n\n" "127\n" "127.0\n" "127.0.0\n" "127.0.0.1\n\n" ".127\n" ".127.0\n" ".127.0.0\n" ".127.0.0.1\n\n" "8.8.8.8\n" "8.8.4.4\n\n" "c:/\n" "c:/foo/\n" "c:/foo/bar/\n\n" "\\\\\n" "\\\\foo\n" "\\\\foo.bar\n" "\\\\foo\\bar\n\n" "http://regexp101.com\n" "regexp101.com\n" "www.regexp101.com\n" "www.regexp101.com/") matches = regex.finditer(test_str) for match_num, match in enumerate(matches, start=1): print(f"Match {match_num} was found at {match.start()}-{match.end()}: {match.group()}") for group_num, group in enumerate(match.groups(), start=1): print(f"Group {group_num} found at {match.start(group_num)}-{match.end(group_num)}: {group}")

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