Regex

import re

Raw string

r'\s*'

Special Characters

.
^, $
{m}
{m, n},{m, n}?
*, *?: {0, INF}
+, +?: {1, INF}
?, ??: {0, 1}

\
[], [^]: character set, auto-escape special chars.
|
(): group, use \number to catch (start from 1)
(?#...): comment
(?=...): lookahead assertion
(?!...): negative lookahead assertion

(?<=...): lookbehind assertion
(?<!...): negative lookbehind assertion

\s: [ \t\n\r\f\v]
\S: [ ^ \t\n\r\f\v]

\w: [a-zA-Z0-9_]

\W: [ ^a-zA-Z0-9_]

API

# search, anywhere
re.search(pattern, string) -> Match-Obj/None
# match, search from start
re.match(pattern, string) -> Match-Obj/None
# fullmatch, search from start to end (full)
re.fullmatch(pattern, string) -> Match-Obj/None
# split
re.split(pattern, string, maxsplit=0) -> list
# findall, finditer
re.findall(pattern, string) -> tuple
# sub
re.sub(pattern, repl, string, count=0) -> string
# escape
re.escape(string) -> string
# compile -> Pattern Object
prog = re.compile(pattern)
res = prog.match(string)
# Match Object
m.groups()
m.group(i)
m.pos
m.endpos

Examples

## extract content inside parenthesis
re.findall('\((.*?)\)', 'a(b), c (de), f(g(h))')
#['b', 'de', 'g(h']

## split by any space
re.split('\s*', 'a b    c\t d')
#['a', 'b', 'c', 'd']