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"(?P<preceeding>^(?P<whitespace>(?:[ ]{4}|\t)+)(?!self\.)(?P<attrprefix>[a-z0-9_\.]{1,})?(?P<clsattrname>[A-Z_]{1,}): )(?P<annotation>(?!ClassVar)(?:[A-Za-z0-9_]+\.*)+(?:(?:(?:\[?[A-Za-z0-9_]+(?:, | \| )?)+(?:\.{3})?)*(?:\]*))*)+(?P<remainder>.*?$[\r\n])" test_str = ("# Regex:\n" "regex_str = r\"(?P<preceeding>^(?P<whitespace>(?:[ ]{4}|\\t)+)(?!self\\.)(?P<attrprefix>[a-z0-9_\\.]{1,})?(?P<clsattrname>[A-Z_]{1,}): )(?P<annotation>(?!ClassVar)(?:[A-Za-z0-9_]+\\.*)+(?:(?:(?:\\[?[A-Za-z0-9_]+(?:, | \\| )?)+(?:\\.{3})?)*(?:\\]*))*)+(?P<remainder>.*?$[\\r\\n])\"\n\n" "#pycharm_compatible_version = (?<preceeding>^(?<whitespace>(?:[ ]{4}|\\t)+)(?!self\\.)(?<attrprefix>[a-z0-9_\\.]{1,})?(?<clsattrname>[A-Z_]{1,}): )(?<annotation>(?!ClassVar)(?:[A-Za-z0-9_]+\\.*)+(?:(?:(?:\\[?[A-Za-z0-9_]+(?:, | \\| )?)+(?:\\.{3})?)*(?:\\]*))*)+(?<remainder>.*?$[\\r\\n])\n\n" "# WARNINGS\n" "# - Top-level functions and local constants are capture as well if they are written in SCREAMING_SNAKE style!\n" "#Assumes:\n" "# - Class variables are named according to SCREAMING_SNAKE convention.\n" "# - Functions and attributes are named according to underscored_lowercase convention.\n" "# - Indent -> 4 spaces or 1 tab per level.\n" "# Notes:\n" "# - Unannotated variables are skipped\n" "# - In PyCharm IDE regex replace; replace occurences of ?P< with ?<\n\n" "import pathlib, os\n" "TOPLEVEL_CONSTANT: str = 'nomatch' # No match\n\n" "class TestAttr:\n" " class TestAttrNested:\n" " underscore_test = 'asdf'\n\n" "class SomeClass(ParentClass, SomeMixin):\n" " FOO_CLS_ATTR: Union[str, int] = 'foo' # Regex should match\n" " BAR_CLS_ATTR: Sequence[tuple[int, ...]] = ((1, 2), (3, 4)) # Regex should match\n" " ANNOTATION_AS_ATTR_ATTR: TestAttr.TestAttrNested.underscore_test = 'asdf' # Regex should match\n" " FIZZ_CLS_ATTR: ClassVar[bool] = True # No match\n" " BUZZ_CLS_ATTR = 10 # No match (not annotated)\n" " \n" " def __init__(self):\n" " local_instance_attribute: float = 1337.420 # No match\n" " self.instance_attribute: str = 'NO_MATCH_PLEASE'\n\n" " class NestedClass:\n" " NESTED_ATTR: str = 'nested_attribute'\n" " \n" " @classmethod\n" " def nested_method(cls):\n" " cls.NESTED_ATTR: str = 'should_match' # Regex should match\n" " print(\"Nested lvl 1!\")\n" " def arbitrarilyy_nested_func(obj):\n" " obj.a.b.c.d.ARBITRARILY_NESTED_ATTR: str = 'nested' # Regex should match\n\n" " @classmethod\n" " def some_method(cls):\n" " cls.FOO_CLS_ATTR: str = 'foo' # Regex should match\n" " cls.instance_attribute.OTHER_CLASATTR: str = 'foo' # Regex should match\n" " print(cls.FOO_CLS_ATTR) # No Match\n\n" "def toplevel_func(arg1: int, CONST_ARG: int = 10) -> int: # No match\n" " MULTIPLIER: float = 6.9\n" " # ^^ Warning! Constants in top-level functions are captured as well! \n" " # ^^ Python doesn't support subpatterns AFAIK.\n" " return arg1*MULTIPLIER\n\n" "### --> after replacing by ${preceeding}ClassVar[${annotation}]${remainder} ###\n\n" "class SomeClass(ParentClass, SomeMixin):\n" " FOO_CLS_ATTR: ClassVar[str] = 'foo' # Regex matches\n" " BAR_CLS_ATTR: ClassVar[Sequence[int]] = (1, 2, 3)\n" " FIZZ_CLS_ATTR: ClassVar[bool] = True\n" " BUZZ_CLS_ATTR = 10 # No match (not annotated)\n" " instance_attribute: float = 1337.420\n\n" " class NestedClass:\n" " NESTED_ATTR: ClassVar[str] = 'nested_attribute'\n" " \n" " @classmethod\n" " def nested_method(cls):\n" " cls.NESTED_ATTR: ClassVar[str] = 'should_match'\n" " print(\"Nested lvl 1!\")\n" " def arbitrarilyy_nested_func(obj):\n" " obj.a.b.c.d.ARBITRARILY_NESTED_ATTR: ClassVar[str] = 'nested'\n\n" " @classmethod\n" " def some_method(cls):\n" " cls.FOO_CLS_ATTR: ClassVar[str] = 'foo' # Regex matches\n" " cls.instance_attribute.OTHER_CLASATTR: ClassVar[str] = 'foo'\n" " print(cls.FOO_CLS_ATTR) # No Match\n\n" "def toplevel_func(arg1: int, CONST_ARG: int = 10) -> int\n" " MULTIPLIER: ClassVar[float] = 6.9 \n" " # ^^ ERRONEOUSLY ADJUSTED...\n" " # ^^ Warning! Constants in top-level functions are captured as well! \n" " # ^^ Python doesn't support subpatterns AFAIK.\n" " return arg1*MULTIPLIER") 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