Michael Bayer wrote:

I tried adapting your example, which admittedly works :-), to a scenario that better resembles mine, but now the property is overriden simply, even when I use ``exclude_properties``.

Note that the setup is overly complex, but this should be seen in the light of a larger setup (as you've previously guided me towards, incidentally).

from sqlalchemy import * from sqlalchemy.orm import *

e = create_engine('sqlite://') m = MetaData(e)

t1= Table( 't1', m, Column('id', Integer, primary_key=True), Column('col', String(50)), ) t1.create()

t2= Table( 't2', m, Column('id', Integer, ForeignKey("t1.id"), primary_key=True), Column('data', String(50)), ) t2.create()

class T1(object): pass

class T2(T1): @property def col(self): return u"Some read-only value."

polymorphic = ( [T2], t1.join(t2))

mapper(T1, t1) mapper( T2, t2, exclude_properties=('col',), with_polymorphic=polymorphic, inherits=T1, inherit_condition=(t1.c.id==t2.c.id), )

sess = sessionmaker()() x = T2()

assert type(T2.col) is property

x.data = "some data" sess.save(x) sess.commit() sess.clear()

assert sess.query(T2).one().data == "some data" assert sess.query(T2).one().col == u"Some read-only value."

x = sess.query(T2).one() x.data = "some new data" sess.commit() assert sess.query(T2).one().data == "some new data"

\malthe