python - model and instance methods: session aware (sqlalchemy) -


so, using , learning sqlalchemy.

i have instance, need value. if value exists, return it. if not calculate , return it.

invariably 'you're doing wrong' , input on improvement appreciated in general. looking how can without explicitly having manage session, because i'm working on starting grow, , managing session when want update instance problematic. makes me think am in fact doing wrong.

so how fix method below not have manage session explicitly? 

def method(self, session):         if self.i_needed_this none:             self.i_needed_this = calculate(calcutron)             session.add(self)             session.commit()             return self.i_needed_this                                 else:             return self.i_needed_this

maybe question should titled 'making instances session aware i'm not explicitly managing it', , if it's dumb question, @ least show me why examples , point me others have asked better.

edit: apparently, importing session i'm using works, , available, maybe non issue or future 1 when more skilled sqlalchemy.

your question common, answer in session asked questions of sa documentation:

  • how can session object? use object_session() classmethod available on session:
    session = session.object_session(someobject)

however, assumes object persistent , either new (but added session already) or bound session. sample code contains logic add object session, assumption might not true in case.


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