Regex Cheatsheet

This cheat sheet can also be found in Happypanda Settings -> About -> Regex Cheatsheet

Characters I

Expression	Meaning
.	Match any character except newline
^	Match the start of the string
$	Match the end of the string
*	Match 0 or more repetitions
+	Match 1 or more repetitions
?	Match 0 or 1 repetitions

Special Sequences I

Expression	Meaning
\A	Match only at start of string
\b	Match empty string, only at beginning or end of a word
\B	Match empty string, only when it is not at beginning or end of word
\d	Match digits # same as [0-9]
\D	Match any non digit # same as [^0-9]

Characters II

Expression	Meaning
*?	Match 0 or more repetitions non-greedy
+?	Match 1 or more repetitions non-greedy
??	Match 0 or 1 repetitions non-greedy
\	Escape special characters
[]	Match a set of characters
[a-z]	Match any lowercase ASCII letter
[lower-upper]	Match a set of characters from lower to upper
[^]	Match characters NOT in a set
A|B	Match either A or B regular expressions (non-greedy)

Special Sequences II

Expression	Meaning
\s	Match whitespace characters # same as [ \t\n\r\f\v]
\S	Match non whitespace characters #same as [^ \t\n\r\f\v]
\w	Match unicode word characters # same as [a-zA-Z0-9_]
\W	Match any character not a Unicode word character # same as [^a-zA-Z0-9_]
\Z	Match only at end of string

Characters III

Expression	Meaning
{m}	Match exactly m copies
{m,n}	Match from m to n repetitions
{,n}	Match from 0 to n repetitions
{m,}	Match from m to infinite repetitions
{m,n}?	Match from m to n repetitions non-greedy (as few as possible)

Groups I

Expression	Meaning
(match)	Use to specify a group for which match can be retrieved later
(?:match)	Non-capturing version parenthesis (match cannot be retrieved later)
(?P)	Capture group with name "name"
(?P=name)	Back reference group named "name" in same pattern
(?#comment)	Comment

Lookahead / Behind I

Expression	Meaning
(?=match)	Lookahead assertion - match if contents matches next, but don't consume any of the string.
(?!match)	Negative lookahead assertion - match if contents do not match next
(?<=match)	Positive lookbehind assertion - match if current position in string is preceded by match
(?<!match)	Negative lookbehind assertion - match if current position is not preceded by match
(?(id/name)yes|no)	Match "yes" pattern if id or name exists, otherwise match "no" pattern