How can I mass-assign SA ORM object attributes?

Question

Hello there,

I have an ORM mapped object, that I want to update. I have all attributes validated and secured in a dictionary (keyword arguments). Now I would like to update all object attributes as in the dictionary.

for k,v in kw.items():
    setattr(myobject, k, v)

doesnt work (AttributeError Exception), thrown from SQLAlchemy.

myobject.attr1 = kw['attr1']
myobject.attr2 = kw['attr2']
myobject.attr3 = kw['attr3']

etc is horrible copy paste code, I want to avoid that.#

How can i achieve this? SQLAlchemy already does something similar to what I want to do in their constructors ( myobject = MyClass(**kw) ), but I cant find that in all the meta programming obfuscated crap in there.

error from SA:

<<          if self.trackparent:
                   if value is not None:
                       self.sethasparent(instance_state(value), True)
                   if previous is not value and previous is not None:
                       self.sethasparent(instance_state(previous), False)
>>  self.sethasparent(instance_state(value), True)
AttributeError: 'unicode' object has no attribute '_sa_instance_state'

Answer 1

myobject.__dict__.update(**kw)

Answer 2

You are trying to assign a unicode string to a relation attribute. Say you have:

 class ClassA(Base):
     ...
     b_id = Column(None, ForeignKey('b.id'))
     b = relation(ClassB)

And you are trying to do:

 my_object = ClassA()
 my_object.b = "foo"

When you should be doing either:

 my_object.b_id = "foo"
 # or
 my_object.b = session.query(ClassB).get("foo")