1 

     2 class RelationTags(object):

     3 

     4     def __init__(self, use_set=False):

     5         self.use_set = use_set

     6         self._tagdefs = {}

     7         

     8     def set_rtag(self, tag, role, rtype, stype='*', otype='*'):

     9         assert not self.use_set

    10         assert role in ('subject', 'object'), role

    11         self._tagdefs[(stype, rtype, otype, role)] = tag

    12         

    13     def rtag(self, role, rtype, stype='*', otype='*'):

    14         assert not self.use_set

    15         for key in reversed(self._get_keys(role, rtype, stype, otype)):

    16             try:

    17                 return self._tagdefs[key]

    18             except KeyError:

    19                 continue

    20         return None

    21         

    22     def etype_rtag(self, etype, role, rtype, ttype='*'):

    23         if role == 'subject':

    24             return self.rtag(role, rtype, etype, ttype)

    25         return self.rtag(role, rtype, ttype, etype)

    26         

    27     def add_rtag(self, tag, role, rtype, stype='*', otype='*'):

    28         assert self.use_set

    29         assert role in ('subject', 'object'), role

    30         rtags = self._tagdefs.setdefault((stype, rtype, otype, role), set())

    31         rtags.add(tag)

    32         

    33     def rtags(self, role, rtype, stype='*', otype='*'):

    34         assert self.use_set

    35         rtags = set()

    36         for key in self._get_keys(role, rtype, stype, otype):

    37             try:

    38                 rtags.update(self._tagdefs[key])

    39             except KeyError:

    40                 continue

    41         return rtags

    42         

    43     def etype_rtags(self, etype, role, rtype, ttype='*'):

    44         if role == 'subject':

    45             return self.rtags(role, rtype, etype, ttype)

    46         return self.rtags(role, rtype, ttype, etype)

    47 

    48     def _get_keys(self, role, rtype, stype, otype): 

    49         assert role in ('subject', 'object'), role

    50         keys = [('*', rtype, '*', role),

    51                 ('*', rtype, otype, role),

    52                 (stype, rtype, '*', role),

    53                 (stype, rtype, otype, role)]

    54         if stype == '*' or otype == '*':

    55             keys.remove(('*', rtype, '*', role))

    56             if stype == '*':

    57                 keys.remove(('*', rtype, otype, role))

    58             if otype == '*':

    59                 keys.remove((stype, rtype, '*', role))            

    60         return keys

    61     

    62     # dict compat

    63     def __getitem__(self, key):

    64         if isinstance(key, basestring):

    65             key = (key,)

    66         return self.rtags(*key)

    67 

    68     __contains__ = __getitem__