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. |