python - Problem with sqlAlchemy model -

so have following situation. have class datatypes has following structure:

class datatype(base):     __tablename__ = 'data_types'     id = column(integer, primary_key=true)     type_name = column(string)     fk_result_storage = column(integer, foreignkey('data_storages.id'))      parentdatastorage = relationship("datastorage", backref=backref("datatype",    cascade="all,delete"))      def __init__(self, name, resultid):        self.type_name = name        self.fk_result_storage = resultid 

now relationship defined here works. have specific data types created dynamically trough introspection , need deleted cascaded also. created this:

t = table('data_' + obj.__name__.lower(), *t[:-1], **t[-1]) mapper(obj, t, *args, **kwargs) model.base.metadata.create_all(dao.engine)    

this works fine , tables created needed. want add relationship similar 1 datatype class. tried this:

t = t('data_' + obj.__name__.lower(), *t[:-1], **t[-1]) m(obj,t,properties = {'children' : relationship('datatype', backref=backref(obj, cascade="all,delete"))} )    model.base.metadata.create_all(dao.engine) 

but gives me:

 sqlalchemy.exc.invalidrequesterror: 1 or more mappers failed initialize - can't proceed initialization of other mappers.  original exception was: relationship 'children' expects class or mapper argument (received: <type 'str'>) 

i`m quite new sqlalchemy. suggestions ?

regards, bogdan

sqlalchemy not strongest skill, think property wrong:

properties = {'children' : relationship('datatype', backref=backref(obj, cascade="all,delete"))} 

i think should be:

properties = {'children' : relationship(datatype, backref=backref(obj, cascade="all,delete"))} 

i.e., reference datatype class, not string.