15.3. REs and Python

Now that we know all about regular expressions, we can examine how Python currently supports regular expressions through the re module. The re module was introduced to Python in version 1.5. If you are using an older version of Python, you will have to use the now-obsolete regex and regsub modules—these older modules are more Emacs-flavored, are not as full-featured, and are in many ways incompatible with the current re module.

However, regular expressions are still regular expressions, so most of the basic concepts from this section can be used with the old regex and regsub software. In contrast, the new re module supports the more powerful and regular Perl-style (Perl5) REs, allows multiple threads to share the same compiled RE objects, and supports named subgroups. In addition, there is a transition module called reconvert to help developers move from regex/regsub to re. However, be aware that although there are different flavors of regular expressions, we will primarily focus on the current incarnation for Python.