regex module

The (?:...) notation should be fairly popular; with it, you can group
parts of a regex, but it does not save them for future retrieval or use. This
comes in handy when you don’t want superfluous matches that are saved
and never used:


>>> re.findall(r'http://(?:\w+\.)*(\w+\.com)',
...
'http://google.com http://www.google.com http://
code.google.com')
['google.com', 'google.com', 'google.com']