Hi.
I am having some trouble understanding how to use native python data
types with hybrid properties. I have the following model. I am using
flask-sqlalchemy however I run into the same issue in straight
sqlalchemy too.
class SystemModel(BaseModel):
__tablename__ = 'system'
class_number = DB.Column(DB.Integer, DB.ForeignKey(
ClassModel.get_fk('number')), primary_key=True)
name = DB.Column(DB.String, nullable=False)
_ports = DB.Column('ports', DB.String)
# ports is stringified [(port, proto, mapped_port), ... ]
@hybrid_property
def ports(self):
if self._ports:
return ast.literal_eval(self._ports) <-- problem here
return None <-- also here
@ports.setter
def ports(self, value):
self._ports = str(value)
I run into trouble when using this in a query:
results = SystemModel.query.with_entities(SystemModel.ports).filter(
SystemModel.ports != None).all()
So the problem of course is that self._ports is not really a string so
literal_eval fails. I think I can use sqlalchemy.literal here but am not
sure if that will help in this case or how exactly to use it.
I realize that the right way would be to have a separate ports table
with the system pk being the fk+pk and then using it and I will probably
go down that road, however I would still like to understand what exactly
is going on here.
I did read:
http://techspot.zzzeek.org/2011/10/21/hybrids-and-value-agnostic-types/
and can certainly go down that road too, however it seems a bit of
overkill for what I really want.
Any help would be greatly appreciated.
Thanks
AM
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