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""" # SETTINGS (?<ANCHORED>){1} (?<NO_SIGN_DUP>){1} (?<PYTHON_POW>){1} (?<COMMENTS>){0} (?(ANCHORED)^(?&s)*) (?(DEFINE) (?<s>(?(COMMENTS)(?:\s+|\/\*[\s\S]*?\*\/|\/\/.*|\#.*)|\s+)) (?<sign>(?(NO_SIGN_DUP)(?<=(?<_>[\s\S]))(?!(?P=_)))[-+]) (?<base>\d+(?:\.\d*)?|\d*\.\d+) (?<exp>(?:[eE][+-]?\d+)) (?<num>(?&sign)?(?&base)(?&exp)?(?!\w)) (?<bracketed>\((?&s)*(?&expr)(?&s)*\)) (?<atom>(?&num)|(?&bracketed)) (?<pow>(?&atom)(?:(?&s)*(?(PYTHON_POW)(?:\^|\*\*)|\^)(?&s)*(?&pow))*) (?<mul>(?&pow)(?:(?&s)*[*\/](?&s)*(?&mul))*) (?<add>(?&mul)(?:(?&s)*[+-](?&s)*(?&add))*) (?<expr>(?&add)) ) (?&expr) (?(ANCHORED)(?&s)*$) """, flags=re.VERBOSE | re.MULTILINE) test_str = ("0\n" "::\n" "1\n" "::\n" "+1\n" "::\n" "-1\n" "::\n" "1.e-1\n" "::\n" "1e1\n" "::\n" ".1e+1\n" "::\n" "-6*((2**(2+4))/3)\n" "::\n" "0*0\n" "::\n" "0+0\n" "::\n" "0/0\n" "::\n" "0^0\n" "::\n" "0**0\n" "::\n" "0-0\n" "::\n" "5 - -2\n" "::\n" "5- -2\n" "::\n" "5+-2\n" "::\n" ".1\n" "::\n" "1.\n" "::\n" "1.1\n" "::\n" " -2\n" "::\n" "5 * (2 + 5 /* comment */ // )\n" " - 1)\n\n" "INVALID: // Separated by :: to prevent parsing multiple examples\n" ".\n" "::\n" "1e\n" "::\n" "1e+\n" "::\n" "1e-\n" "::\n" "e2\n" "::\n" "+\n" "::\n" "-\n" "::\n" "5 --2\n\n") 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