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.