Regex

import re
python

Raw string

r'\s*'
python

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
python

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']
python