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"(?<!\d)(?<!_)(?<![a-zA-z])string(?!\d)(?!_)(?![a-zA-Z])", flags=re.MULTILINE) test_str = ("module mpi_hello_world\n" " use mpi\n" " implicit none\n" "contains\n" " subroutine hello_world(size, & ! testtest\n" " & r_ank, &!\n" " & myhostname &\n" " & )\n" "! this is a comment\n" " ! this also\n" " integer, intent(in) :: size, rank23, rank_er,ranking, myrank, my2r_ank\n" " character(len = *), intent(out) :: myhostname\n\n" " integer :: stat\n" " \n" " myhostname = \"(no host name)\"\n" "#ifdef __INTEL_COMPILER\n" " call get_environment_variable(\"COMPUTERNAME\", myhostname)\n" "#else\n" " stat = hostnm(myhostname)\n" "#endif \n\n" " write(*, *) \"Hello world FORTRAN rank:\", rank, \" size:\", size, &\n" " & \"hostname:\", trim(myhostname)\n" " \n" " end subroutine hello_world\n" "end module mpi_hello_world\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