This module provides regular expression matching operations
similar to those found in Perl. Regular expression pattern
strings may not contain null bytes, but can specify the null
byte using the \number notation. Both patterns and strings to be
searched can be Unicode strings as well as 8-bit strings. The re
module is always available. Regular expressions use the
backslash character ("\") to indicate special forms or to allow
special characters to be used without invoking their special
meaning. This collides with Python's usage of the same character
for the same purpose in string literals; for example, to match a
literal backslash, one might have to write '\\\\' as the pattern
string, because the regular expression must be "\\", and each
backslash must be expressed as "\\" inside a regular Python
string literal. The solution is to use Python's raw string
notation for regular expression patterns; backslashes are not
handled in any special way in a string literal prefixed with
"r". So r"\n" is a two-character s