extend Python namedtuple with many @properties?

Question

How can namedtuples be extended or subclassed with many additional @properties ?
For a few, one can just write the text below; but there are many, so I'm looking for a generator or property factory. One way would be to generate text from _fields and exec it; another would be an add_fields with the same effect at runtime.
(My @props are to get rows and fields in a database scattered across several tables, so that rec.pname is persontable[rec.personid].pname; but namedtuples-with-smart-fields would have other uses too.)

""" extend namedtuple with many @properties ? """
from collections import namedtuple

Person = namedtuple( "Person", "pname paddr" )  # ...
persontable = [
    Person( "Smith", "NY" ),
    Person( "Jones", "IL" )
    ]

class Top( namedtuple( "Top_", "topid amount personid" )):
    """ @property 
        .person -> persontable[personid]
        .pname -> person.pname ...
    """
    __slots__ = ()
    @property
    def person(self):
        return persontable[self.personid]

    # def add_fields( self, Top.person, Person._fields ) with the same effect as these ?
    @property
    def pname(self):
        return self.person.pname
    @property
    def paddr(self):
        return self.person.paddr
    # ... many more

rec = Top( 0, 42, 1 )
print rec.person, rec.pname, rec.paddr

Answer 1

The answer to your question

How can namedtuples be extended or subclassed with additional @properties ?

is: exactly the way you're doing it! What error are you getting? To see a simpler case,

>>> class x(collections.namedtuple('y', 'a b c')):
...   @property
...   def d(self): return 23
... 
>>> a=x(1, 2, 3)
>>> a.d
23
>>> 

Answer 2

How about this?

class Top( namedtuple( "Top_", "topid amount personid" )): 
    """ @property  
        .person -> persontable[personid] 
        .pname -> person.pname ... 
    """ 
    __slots__ = () 
    @property 
    def person(self): 
        return persontable[self.personid] 

    def __getattr__(self,attr):
        if attr in Person._fields:
            return getattr(self.person, attr)
        raise AttributeError("no such attribute '%s'" % attr)