import re
regex_patern = ur'([\(\[](?P<event>[^\()\)\]]*)[\)\]])?\s*([\(\[](?P<type>[^\)\](\)\])]*)[\)\]])?\s*(\[(?P<group>[^\(\]]*)(\((?P<artist>[^\)]*)\))?\])?(?P<title>[^\(\)\[\]]*)([\(\[](?P<from>[^\)\]]*)[\)\]])?\s*([\(\[](?P<more1>[^\)\]]*)[\)\]])?'

p = re.compile (regex_patern )

rows= [
'(event ) (tag ) [group (artist )] title (form ) [addition1] [addition2]',
'(event ) [group (artist )] title (form ) [addition1]',
'[event] [group (artist )] title (form ) (addition1 )',
'(tag ) [group (artist )] title',
'[group (artist )] title',
'title',
]

for r in rows:
r = re.search (p, r )
print r.groupdict ()

完全改好了，你有两个地方不对，一个是最后边那个地方强制捕获了，一个是不能让 event 捕获 [group (artist )]，所以在 event 那个段里边要改成最后\(也放弃。

$ python re.py
{u'from': 'form ', u'more1': 'addition1', u'artist': 'artist ', u'title': ' title ', u'group': 'group ', u'type': 'tag ', u'event': 'event '}
{u'from': 'form ', u'more1': 'addition1', u'artist': 'artist ', u'title': ' title ', u'group': 'group ', u'type': None, u'event': 'event '}
{u'from': 'form ', u'more1': 'addition1 ', u'artist': 'artist ', u'title': ' title ', u'group': 'group ', u'type': None, u'event': 'event'}
{u'from': None, u'more1': None, u'artist': 'artist ', u'title': ' title', u'group': 'group ', u'type': None, u'event': 'tag '}
{u'from': None, u'more1': None, u'artist': 'artist ', u'title': ' title', u'group': 'group ', u'type': None, u'event': None}
{u'from': None, u'more1': None, u'artist': None, u'title': 'title', u'group': None, u'type': None, u'event': None}