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
No Match

r"
"
gm

Test String

Code Generator

Language

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r"\b(?<=\w)\s{20}" test_str = ("Ateles_geoffroyi GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Ateles_hybridus GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Ateles_fusciceps GATGAGTGTGGCAAGGCCCAAGCGGAAGTGC??????????\n" "Ateles_chamek GATGAGTGTGGCAAGGCCCA?????????????????????\n" "Ateles_paniscus ?????????????????????????????????????????\n" "Brachyteles_arachnoides GATGAGTGTGGCAAGGCCCAAGCGGAAGT????????????\n" "Brachyteles_hypoxanthus GATGAGTGTGGCAAG??????????????????????????\n" "Lagothrix_cana GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Lagothrix_lagotricha GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Alouatta_belzebul ?????????????????????????????????????????\n" "Alouatta_caraya ?????????????????????????????????????????\n" "Alouatta_sara GATGAATGTGGCAAGGCCCAAGCAGAAGTGCCG--GTTGCT\n" "Alouatta_palliata GATGAATGTGGCAAGGCCCAAGCAGAAGTGCCG--GTTGCT\n" "Callicebus_brunneus ?????????????????????????????????????????\n" "Callicebus_moloch GATGAGTGTGGCAAGGCCCAAGCAGAAGTGCCG--G?????\n" "Callicebus_cupreus GATGAGTGTGGCAAGGCCCAAGCAGAAGTGCCG--GTTGCT\n" "Callicebus_caligatus GATGAGTGTGGCAAGGCCCAAGCAGAAGTGCCG--GTTGCT\n" "Callicebus_donacophilus GATGAGTGTGGCAAGGCCCAAGCAGAAGTGCCG--GTTGCT\n" "Callicebus_coimbrai GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Callicebus_personatus GATGAGTGTGGCAAGGCCCAAGCGGAA??????????????\n" "Callicebus_nigrifrons GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Cacajao_melanocephalus GATGAGTGTGGCAAAGCCCA?????????????????????\n" "Cacajao_calvus GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Chiropotes_israelita GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Chiropotes_satanas_chiro ?????????????????????????????????????????\n" "Pithecia_irrorata GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--G?????\n" "Pithecia_pithecia GATGAGTGTGGCAAGGCCCAAGCGGAAGTGCCG--GTTGCT\n" "Tarsius_bancanus ?????????????????????????????????????????\n" "Tarsius_syrichta ?????????????????????????????????????????\n" "Lepilemur_ankaranensis AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Lepilemur_septentrionali AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Lepilemur_dorsalis AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Lepilemur_ruficaudatus AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Lepilemur_jamesi AACGAGTGTGGCAAGGCCCAGG???????????????????\n" "Microcebus_murinus_subsp AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Microcebus_murinus_subsp ?????????????????????????????????????????\n" "Mirza_zaza AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Cheirogaleus_medius ?????????????????????????????????????????\n" "Propithecus_verreauxi_co ?????????????????????????????????????????\n" "Propithecus_verreauxi AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Propithecus_tattersalli AACGAGTGTGGCAAGGCCCAGGCTGAAGTTCCG--GTTGCT\n" "Propithecus_diadema AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Propithecus_edwardsi AACGAGTGTGGCAAGGCCCAGGCG?????????????????\n" "Avahi_laniger AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_rufus AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_collaris AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_fulvus AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_albifrons AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_sanfordi AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_mongoz AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_macaco AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_macaco_flavifron AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_coronatus AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Eulemur_rubriventer AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Hapalemur_occidentalis AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Hapalemur_griseus AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Lemur_catta AACGAGTGTGGCAAGGCCCAGGCGGAAGTTCCG--GTTGCT\n" "Varecia_variegata_varieg AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Varecia_variegata_rubra AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Daubentonia_madagascarie ?????????????????????????????????????????\n" "Nycticebus_bengalensis AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Nycticebus_coucang AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Nycticebus_pygmaeus AACGAGTATGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Loris_tardigradus AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Arctocebus_calabarensis AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Perodicticus_potto AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Otolemur_garnetti AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Otolemur_crassicaudatus AACGAGTGTGGCAAGGCCCAGGCAGAAGTTCCG--GTTGCT\n" "Galago_moholi ?????????????????????????????????????????\n" "Galago_senegalensis ?????????????????????????????????????????\n" "Galago_thomasi AACGAGTGTGGCAAGGCCCAGGCG?????????????????\n" "Galeopterus_variegatus GATGAGTGTGGCAAGGCCCAAGCAGAAGTTCCG--G?????\n" "Cynocephalus_volans GATGAGTGTGGCAAGGCCCAAGCAGAAGTCCCG--GTTGCT\n" "Tupaia_glis ?????????????????????????????????????????\n" "Tupaia_minor ?????????????????????????????????????????\n" "rabbit_rabbit_rabbit ?????????????????????????????????????????\n") matches = re.finditer(regex, test_str, re.MULTILINE) for matchNum, match in enumerate(matches, start=1): print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group())) for groupNum in range(0, len(match.groups())): groupNum = groupNum + 1 print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum))) # Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

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