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]
  • Character class intersection
    [\w&&[^\d]]
  • 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"^[a-zA-Z]\d{4}(-[a-zA-Z0-9]{2})?$", flags=re.MULTILINE) test_str = ("# The CMS, who maintain these codes, describe the format as:-\n" "# \"HCPCS Level II codes (also known as alpha-numeric codes) consist of a single alphabetical letter followed by 4 numeric digits.\"\n" "# (https://www.cms.gov/medicare/coding-billing/healthcare-common-procedure-system)\n" "# NOTE: This regex will not identify HCPCS Level I codes (AKA CPT codes)\n" "# Also, some sources say the single letter ranges only from A-V (this regex follows A-Z)\n" "# It's not clear if the first letter must be capitalized. This regex assumes not.\n" "# This version of the regex matches optional modifiers (ie a hyphen then 2 characters after the code)\n" "# (https://www.aapc.com/resources/what-are-medical-coding-modifiers)\n" "# A separate regex has been created on regex101 that ignores modifiers\n\n" "# Genuine code patterns\n" "E8015\n" "A6410\n" "C5278\n" "G2102\n" "M1221\n" "V2623\n" "V2756\n" "c5278\n" "g2102\n" "m1221\n" "v2623\n" "v2756\n" "G2102-23\n" "E8015-OK\n" "V2756-L5\n" "V2756-5Q\n\n" "# Should fail\n" "EE8015\n" "6410\n" "E641O\n" "[6410\n" "_6510\n" "g212\n" "C52789\n" "G2101-\n" "G2101-2\n" "G2101-K\n" "G2101-OKK\n" "G2101-123\n" "G2101-!!\n" "G2101-!1\n" "G2101-()") 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