\\

escape special characters

.

matches any character

^

matches beginning of string

$

matches end of string

[5b-d]

matches any chars \'5\', \'b\', \'c\' or \'d\'

[^a-c6]

matches any char except \'a\', \'b\', \'c\' or \'6\'

R|S

matches either regex R or regex S

()

creates a capture group and indicates precedence

*

0 or more (append ? for non-greedy)

+

1 or more (append ? for non-greedy)

?

0 or 1 (append ? for non-greedy)

{m}

exactly mm occurrences

{m, n}

from m to n. m defaults to 0, n to infinity

{m, n}?

from m to n, as few as possible

\\A

start of string

\\b

matches empty string at word boundary (between \\w and \\W)

\\B

matches empty string not at word boundary

\\d

digit

\\D

non-digit

\\s

whitespace: [ \\t\\n\\r\\f\\v]

\\S

non-whitespace

\\w

alphanumeric: [0-9a-zA-Z_]

\\W

non-alphanumeric

\\Z

end of string

\\g<id>

matches a previously defined group

(?iLmsux)

matches empty string, sets re.X flags

(?:...)

non-capturing version of regular parentheses

(?P...)

matches whatever matched previously named group

(?P=)

digit

(?#...)

a comment; ignored

(?=...)

lookahead assertion: matches without consuming

(?!...)

negative lookahead assertion

(?<=...)

lookbehind assertion: matches if preceded

(?<!...)

negative lookbehind assertion

(?(id)yes|no)

match \'yes\' if group \'id\' matched, else \'no\'