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"^\s*(#*)\s*(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+([a-zA-Z0-9\.\- ]+)([^#]*#?\w*\s*)$", flags=re.MULTILINE | re.IGNORECASE) test_str = ("# Copyright (c) 1993-2009 Microsoft Corp.\n" "#\n" "# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.\n" "#\n" "# This file contains the mappings of IP addresses to host names. Each\n" "# entry should be kept on an individual line. The IP address should\n" "# be placed in the first column followed by the corresponding host name.\n" "# The IP address and the host name should be separated by at least one\n" "# space.\n" "#\n" "# Additionally, comments (such as these) may be inserted on individual\n" "# lines or following the machine name denoted by a '#' symbol.\n" "#\n" "# For example:\n" "#\n" "# 102.54.94.97 rhino.acme.com # source server\n" "# 38.25.63.10 x.acme.com # x client host\n\n" "# localhost name resolution is handled within DNS itself.\n" "# 127.0.0.1 localhost\n" "# ::1 localhost\n\n" "127.0.0.1 jw smartsite.jw\n" "127.0.0.1 dev.filepresso.com dev.filepresso.com.pl dev.filepresso.pl dev.filefly.pl\n" "#### 89.31.66.248 sp.biatelbit.pl\n\n" "192.168.72.51 subversion.biatel.com.pl\n" " \n" "# 127.0.0.1 bip.smartsite.bit-sa.pl\n" " # 127.0.0.1 bip.augustow.wrotapodlasia.pl\n" "127.0.0.1 rpowp.smartsite.bit-sa.pl\n" "127.0.0.1 cms.smartsite.bit-sa.pl\n" "127.0.0.1 cms-test.smartsite.bit-sa.pl\n\n" "############################################################ \n" "# \n" "# UMWP \n" "# \n" "############################################################ \n\n" "############################################################ \n" "# ST - test - UMWP \n" "############################################################ \n" "#10.200.14.70 ST-sapp1 \n" "#10.200.14.70 tv.smartsite.bit-sa.pl wp.smartsite.bit-sa.pl cms.smartsite.bit-sa.pl test.smartsite.bit-sa.pl bip.smartsite.bit-sa.pl si.smartsite.bit-sa.pl sspw.wrotapodlasia.pl \n" "#10.200.14.70 radny.smartsite.bit-sa.pl stats.smartsite.bit-sa.pl test9.smartsite.bit-sa.pl ") 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