Regular Expression Patterns

Following lists the regular expression syntax that is available in Python.

Pattern	Description
^	match beginning of the line.
$	match end of line.
.	match any single character except '\n'.
[...]	match any single character in brackets.
re*	match 0 or more occurrences of preceding expression
re+	match 1 or more occurrences of preceding expression
re?	match 0 or 1 occurrence of preceding expression.
re{n}	match exactly n number of occurrences of preceding expression.
\1...\9	match n-th grouped sub-expression.
(re)	Groups regular expressions and remembers matched text.

Examples

# \
    
     ) or [text](url "title")LINK_RE = NOIMG + BRK + \    r'''\(\s*(<.*?>|((?:(?:\(.*?\))|[^\(\)]))*?)\s*((['"])(.*?)\12\s*)?\)'''# ![alttxt](http://x.com/) or ![alttxt](
     )IMAGE_LINK_RE = r'\!' + BRK + r'\s*\(\s*(<.*?>|([^"\)\s]+\s*"[^"]*"|[^\)\s]*))\s*\)'# [Google][3]REFERENCE_RE = NOIMG + BRK + r'\s?\[([^\]]*)\]'# [Google]SHORT_REF_RE = NOIMG + r'\[([^\]]+)\]'