Regular Expressions

The following tables provide a overview of the regular expressions syntax. See also Python regular expressions description in the Python re module.

Special Characters	Description
.	Matches any character (dot).
^	“^...”, matches start-of-string (caret).
$	”...$”, matches end-of-string (dollar sign).
|	“A|B”, matches “A” or “B”.
\	Escape character.
\.	EXAMPLE: Matches character ‘.’ (dot).
\\	EXAMPLE: Matches character ‘\‘ (backslash).

To select or match characters from a special set of characters, a character set must be defined.

Character sets	Description
[...]	Define a character set, like [A-Za-z].
\d	Matches digit character: [0-9]
\D	Matches non-digit character.
\s	Matches whitespace character: [ \t\n\r\f\v]
\S	Matches non-whitespace character
\w	Matches alphanumeric character: [a-zA-Z0-9_]
\W	Matches non-alphanumeric character.

A text part must be group to extract it as part (parameter).

Grouping	Description
(...)	Group a regular expression pattern (anonymous group).
\number	Matches text of earlier group by index, like: “\1”.
(?P<name>...)	Matches pattern and stores it in parameter “name”.
(?P=name)	Match whatever text was matched by earlier group “name”.
(?:...)	Matches pattern, but does non capture any text.
(?#...)	Comment (is ignored), describes pattern details.

If a group, character or character set should be repeated several times, it is necessary to specify the cardinality of the regular expression pattern.

Cardinality	Description
?	Pattern with cardinality 0..1: optional part (question mark).
*	Pattern with cardinality zero or more, 0.. (asterisk).
+	Pattern with cardinality one or more, 1.. (plus sign).
{m}	Matches m repetitions of a pattern.
{m,n}	Matches from m to n repetitions of a pattern.
[A-Za-z]+	EXAMPLE: Matches one or more alphabetical characters.