Regular Expressions

Official Documentation

Functions

Function	Description
re.search(r, s)	Looks for a substring of s that matches r
re.match(r, s)	Looks for a prefix s that matches r
re.fullmatch(r, s)	Checks if s matches r in its entirety
re.split(r, s)	Splits s using separators described by r
re.findall(r, s)	Finds all substrings in s matching r
re.sub(r, repl, s)	Replaces all substrings of s matching r by repl

Option	Description
DOTALL	. also matches newlines
MULTILINE	^ and $ also match immediately after and before newlines, respectively	IGNORECASE	Case insensitive matching

Regex Syntax

Character	Description
.	Matches anything except newline (see DOTALL)
^	Matches start of string (see MULTILINE)
$	Matches end of string (see MULTILINE)
p*	0 or more repetitions of p
p+	1 or more repetitions of p
p?	Optional p
p{m}	m repetitions of p
p{m,n}	m to n repetitions of p
p|q	Matches either p or q
[...]	Character class
[^...]	Negated character class
\d	Digit
\D	Nondigit
\w	Word character (letter of underscore)
\W	Nonword character
\b	Word boundary
\s	Whitespace character
\S	Nonwhitespace character
\A	Beginning of string
\Z	End of string
\1, \2, …	Backreferences

Examples

Regex	Description
[01]+	Binary number
[IVXLCDM]+	Roman numberal
-?[1-9]\d*(\.\d*)?	Floating point number
\d{2}/\d{2}/\d{4}	Date (dd/mm/yyyy)
[A-Z][a-z]*	Capitalized word