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+(-[0-9A-Za-z]+|--[A-Za-z0-9][\w-]+)", flags=re.MULTILINE) test_str = ("ignores position args\n" "ignores-this _and_this _2 but-not -a -xvzf -4 -6 -Targ\n" "ignores-echo -----------\n" "ignores-mistaken --a did-you-mean -a\n" " --3-2-pulldown\n" " --3gpp-scan\n" " --64\n" " --802_3-sap\n" " --802_3-type\n" " --90\n" " --abi-call0\n" " --action1\n" " --action9\n" " --appData\n" " --assume-utf16be\n" " --assume-utf16le\n" " --authValue\n" " --aws-sigv4\n" " --background_compression\n" " --btf_encode\n" " --cipherText\n" " --Complain\n" " --contains_enumerator\n" " --data_replicas\n" " --disable-pcre2-8\n" " --disable-pcre2grep-callout\n" " --disable-pcre2grep-callout-fork\n" " --disable-pcre2grep-jit\n" " --dns-ipv4-addr\n" " --dns-ipv6-addr\n" " --do-0x20-encode\n" " --do-x20-encode\n" " --dualprime-mpeg2\n" " --eccpoint-L\n" " --enable-ebcdic-nl25\n" " --enable-never-backslash-C\n" " --enable-pcre2-16\n" " --enable-pcre2-32\n" " --enable-pcre2grep-libbz2\n" " --enable-pcre2grep-libz\n" " --enable-pcre2test-libedit\n" " --enable-pcre2test-libreadline\n" " --entityPath\n" " --expect100-timeout\n" " --exportedData\n" " --filter-A\n" " --filter-AAAA\n" " --filterwin2k\n" " --force-ipv4\n" " --force-ipv6\n" " --force-R5\n" " --force-V4\n" " --Foreground\n" " --fwdownload-mode3\n" " --fwdownload-mode3-max\n" " --fwdownload-mode7\n" " --gb18030\n" " --GBR\n" " --hostpubmd5\n" " --hostpubsha256\n" " --http0\n" " --http1\n" " --http2\n" " --http2-prior-knowledge\n" " --http3\n" " --http3-only\n" " --ignoreDefinites\n" " --importData\n" " --Include\n" " --intra_dc_prec\n" " --ip6\n" " --ip6-destination\n" " --ip6-destination-port\n" " --ip6-dport\n" " --ip6-dst\n" " --ip6-icmp-type\n" " --ip6-proto\n" " --ip6-protocol\n" " --ip6-source\n" " --ip6-source-port\n" " --ip6-sport\n" " --ip6-src\n" " --ip6-tclass\n" " --ipv4\n" " --ipv6\n" " --Iraw\n" " --Istdin\n" " --Istdout\n" " --jsonPolicy\n" " --keep-utf16\n" " --keyPath\n" " --lang_exclude\n" " --Lc\n" " --Lee\n" " --linearize-pass1\n" " --Lmac2\n" " --Ln\n" " --logData\n" " --log-ip6\n" " --Lx\n" " --mirror-above-4G\n" " --mirror-below-4G\n" " --netfilter6\n" " --no-0x20-encode\n" " --no3d\n" " --no-altscan-mpeg2\n" " --no-D\n" " --no-dhcpv4-interface\n" " --no-dummy-svcd-SOF\n" " --nr_methods\n" " --numBytes\n" " --Numeric\n" " --nvPath\n" " --oauth2-bearer\n" " --omit_journal_replay\n" " --output-Z1\n" " --output-Z2\n" " --p12-charset\n" " --pathList\n" " --pathOfKeyToDuplicate\n" " --pcrIndex\n" " --pcrList\n" " --pcrLog\n" " --pcrValue\n" " --plainText\n" " --policyPath\n" " --policyRef\n" " --post301\n" " --post302\n" " --post303\n" " --prefer-ata12\n" " --print0\n" " --PROG-option\n" " --proxy1\n" " --proxy-http2\n" " --proxy-tls13-ciphers\n" " --proxy-tlsv1\n" " --publicKey\n" " --publicKeyPath\n" " --qualifyingData\n" " --quiet-dhcp6\n" " --quoteInfo\n" " --readimpliesX\n" " --reduction-2x2\n" " --reduction-4x4\n" " --replay_journal_only\n" " --searchPath\n" " --seek_bytes\n" " --set-recommended-min_free_kbytes\n" " --S-force\n" " --size_bytes\n" " --socks4\n" " --socks4a\n" " --socks5\n" " --socks5-basic\n" " --socks5-gssapi\n" " --socks5-gssapi-nec\n" " --socks5-gssapi-service\n" " --socks5-hostname\n" " --sslv2\n" " --sslv3\n" " --tls13-ciphers\n" " --tlsv1\n" " --tpm2\n" " --tpm2bPrivate\n" " --tpm2bPublic\n" " --type_trans\n" " --type_transition\n" " --UCS-2\n" " --Version\n" " --warning-exit-0\n" " --Wext\n" " --with-pcre2grep-bufsize\n" " --with-pcre2grep-max-bufsize\n" " --with-PROG\n" " --Wnp\n" " --Wp\n" " --x11\n" " --x32\n" " --x509certData") 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