import re

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',
]

p = re.compile(ur'^(?:(?:^[\[()](?P<event>[^)\]]+)[)\]](?=.+[\])]$)\s)?(?:[(【](?P<tag>(?<=^[(【])[^】)]+(?=.+[\w】]$)|(?<=\)\s\()[^)]+(?=\)\s\[))[】)]\s)?\[(?:(?P<group>[^(\]]+)\s+\((?P<artist>[^)]+)\)\])\s+)?(?P<title>[^(\n)【]+)(?:\s*[\(【](?P<form>[^)】]+)[)】](?:\s*[\[(](?P<add>[^\])]+)[\])])?(?:\s*[\[(](?P<add2>[^\])]+)[\])])?)?$')

for r in rows:
	[m.groupdict() for m in p.finditer(r)]
	print m.groupdict()