Thanks Mike, I oversimplified a little bit (the factory function takes more arguments than self.stops, not part of the Planning class), but if i create the factory with partial I think it will work.
On Monday, November 16, 2020 at 6:16:24 PM UTC+1 Mike Bayer wrote: > I would use a memoized descriptor for that and have it evaluate when > called. > > Amazingly, i can't find public examples of Python memoize decorators that > aren't overwrought. we use one that is completely efficient and simple: > > class memoized_property(object): > """A read-only @property that is only evaluated once.""" > > def __init__(self, fget, doc=None): > self.fget = fget > self.__doc__ = doc or fget.__doc__ > self.__name__ = fget.__name__ > > def __get__(self, obj, cls): > if obj is None: > return self > obj.__dict__[self.__name__] = result = self.fget(obj) > return result > > > then you can just set it up as: > > class Planning(...): > @memoized_property > def matrix(self): > return self.matrix_factor(self.stops) > > > > > On Mon, Nov 16, 2020, at 11:43 AM, lars van gemerden wrote: > > Hi Mike, > > What if during reconstruction you need a one-to-many attribute, like: > > class Planning(SqlaBase): > stops = relationship(*"Stop"*, back_populates=*"planning"*, lazy= > *"joined"*) > > matrix_factory = Matrix > > def __init__(self, **kwargs): > super().__init__(**kwargs) > self.matrix = self.matrix_factory(self.stops) > > @reconstructor > def init_on_load(self): > self.matrix = self.matrix_factory(self.stops) > The docs say self.stops will not be completely loaded in init_on_load, how > could i make this work? > > Cheers, Lars > On Monday, August 7, 2017 at 6:09:08 AM UTC+2 Mike Bayer wrote: > > > > On Aug 6, 2017 1:33 PM, "Shane Carey" <shanec...@gmail.com> wrote: > > Hey Mike, > > I can expand my example. I have an orm mapped attribute like this > > class Obj(Base): > _evaluator = Column(String) > > def __init__(self, **kwargs): > super().__init__(**kwargs) > self._eval_func = eval(self._evaluator) > > @orm.reconstructor > def init_on_load(self): > self._eval_func = eval(self._evaluator) > > @property > def evaluator(self): > return self._eval_func > > @evaluator.setter > def set_evaluator(ev): > self._evaluator = ev > self._eval_func = eval(self._evaluator) > > You can see that I have to explicitly set self._eval_func in three > different places, when really I just want to set it every time > self._evaluator is set. > > It looks to me like the orm events are just a different way of placing the > different settings of this class attribute > > Also, I would like to not call eval in the getter of the property for the > sake of performance (I know that would simplify the issue). > > Is there a way to intercept the setting of self._evaluator for all cases? > > > > Use the init and load event listeners from my previous email on top of one > function. It will be called for init and load. > > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+...@googlegroups.com. > To post to this group, send email to sqlal...@googlegroups.com. > Visit this group at https://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/e9b2b9ff-0979-43be-94f4-fdb3ceb48ae9n%40googlegroups.com > > <https://groups.google.com/d/msgid/sqlalchemy/e9b2b9ff-0979-43be-94f4-fdb3ceb48ae9n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/077d7141-b8dc-46ac-92d8-bee90bd2fb4en%40googlegroups.com.
