Digits:
\d+: Matches one or more digits.\d{4}: Matches exactly four digits.Non-Digits:
\D+: Matches one or more non-digits.Word Characters:
\w+: Matches one or more word characters (alphanumeric characters plus underscore).[a-zA-Z0-9_]+: Equivalent to \w+.Non-Word Characters:
\W+: Matches one or more non-word characters.Whitespace Characters:
\s+: Matches one or more whitespace characters (space, tab, newline).\S+: Matches one or more non-whitespace characters.Line Anchors:
^: Matches the start of a line.$: Matches the end of a line.Character Sets:
[aeiou]: Matches any single character in the set (vowels in this case).[^aeiou]: Matches any single character not in the set (consonants in this case).[a-z]: Matches any single lowercase alphabetical character.Repetitions:
*: Matches zero or more occurrences of the preceding element.+: Matches one or more occurrences of the preceding element.?: Matches zero or one occurrence of the preceding element.{n}: Matches exactly n occurrences of the preceding element.{n,}: Matches n or more occurrences of the preceding element.{n,m}: Matches between n and m occurrences of the preceding element.Alternation:
|: Matches either the pattern before or after the alternation operator.Grouping:
( ): Groups multiple tokens together.Escape Characters:
\: Escapes special characters so they can be treated as literal characters.Quantifiers:
?: Matches zero or one occurrences.*: Matches zero or more occurrences.+: Matches one or more occurrences.{n}: Matches exactly n occurrences.{n,}: Matches at least n occurrences.{n,m}: Matches between n and m occurrences.Anchors:
^: Matches the start of a line.$: Matches the end of a line.\b: Matches a word boundary.\B: Matches a non-word boundary.Character Classes:
[abc]: Matches any single character in the set (a, b, or c).[^abc]: Matches any single character not in the set (any character except a, b, or c).[a-z]: Matches any single lowercase alphabetical character.[A-Z]: Matches any single uppercase alphabetical character.[0-9]: Matches any single digit.Character Escapes:
\.: Matches a literal dot.\^: Matches a literal caret.\$: Matches a literal dollar sign.\(: Matches a literal opening parenthesis.\): Matches a literal closing parenthesis.Quantifiers with Lazy Matching:
*?: Matches zero or more occurrences, but as few as possible.+?: Matches one or more occurrences, but as few as possible.??: Matches zero or one occurrence, but as few as possible.{n,m}?: Matches between n and m occurrences, but as few as possible.Boundary Matchers:
\b: Matches a word boundary.\B: Matches a non-word boundary.\A: Matches the start of the input.\Z: Matches the end of the input, before any newline characters.\z: Matches the end of the input.Lookahead and Lookbehind Assertions:
(?=...): Positive lookahead assertion.(?!...): Negative lookahead assertion.(?<=...): Positive lookbehind assertion.(?<!...): Negative lookbehind assertion.Named Groups:
(?P<name>...): Defines a named capturing group.(?P=name): Matches the same text as the most recent capture group named 'name'.Unicode Character Properties:
\p{...}: Matches any character with the specified Unicode property.\P{...}: Matches any character without the specified Unicode property.Word Boundaries:
\b: Matches a word boundary.\B: Matches a non-word boundary.Matching Specific Quantities:
\d{2,4}: Matches 2 to 4 digits.\w{3,}: Matches 3 or more word characters.\s{1,3}: Matches 1 to 3 whitespace characters.Matching Specific Characters:
[aeiou]{2}: Matches any two consecutive vowels.[0-9a-fA-F]{2}: Matches any two hexadecimal digits.Using Capture Groups:
(\d{3})-(\d{3})-(\d{4}): Matches and captures groups for area code, exchange code, and subscriber number in a phone number.Backreferences:
\1, \2, etc.: Matches the same text as the first, second, etc., capturing group.Matching Any Character:
.: Matches any single character except newline characters.[\s\S]: Matches any character including newline characters.Conditional Matching:
(?(condition)then|else): Matches 'then' if the condition is true, otherwise matches 'else'.