re.sub and empty groups

[Hugo Ferreira]

Hi!

I'm trying to do a search-replace in places where some groups are
optional... Here's an example:

>> re.match(r"Image:([^\|]+)(?:\|(.*))?", "Image:ola").groups()
('ola', None)

>> re.match(r"Image:([^\|]+)(?:\|(.*))?", "Image:ola|").groups()
('ola', '')

>> re.match(r"Image:([^\|]+)(?:\|(.*))?", "Image:ola|ole").groups()
('ola', 'ole')

The second and third results are right, but not the first one, where
it should be equal to the second (i.e., it should be an empty string
instead of None). This is because I want to use re.sub() and when the
group is None, it blows up with a stack trace...

Maybe I'm not getting the essence of groups and non-grouping groups.
Someone care to explain (and, give the correct solution :)) ?

Thanks in advance,

Hugo Ferreira

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