"|" A|B, creates an RE that will match either A or B.
(...) Matches the RE inside the parentheses.
The contents can be retrieved or matched later in the string.
- (?aiLmsux) Set the A, I, L, M, S, U, or X flag for the RE (see below).
+ (?aiLmsux) The letters set the corresponding flags defined below.
(?:...) Non-grouping version of regular parentheses.
(?P<name>...) The substring matched by the group is accessible by name.
(?P=name) Matches the text matched earlier by the group named name.
purge Clear the regular expression cache.
escape Backslash all non-alphanumerics in a string.
-Some of the functions in this module takes flags as optional parameters:
+Each function other than purge and escape can take an optional 'flags' argument
+consisting of one or more of the following module constants, joined by "|".
+A, L, and U are mutually exclusive.
A ASCII For string patterns, make \w, \W, \b, \B, \d, \D
match the corresponding ASCII character categories
(rather than the whole Unicode categories, which is the