How do I raise an exception when assigning to an attribute which is NOT mapped to an SQLAlchemy column?

Question

With SQLAlchemy, I\'m finding that sometimes I mis-type a name of an attribute which is mapped to a column, which results in rather difficult to catch errors:

Answer 1

Override the __get__ method of objects, and check to see if it is in the column (by storing it with the class definition or runtime search)

More information here from SO.

Answer 2

Ok, the solution seems to be to override __setattr__ method of the base class, which allows us to check if the atribute already exists before setting it.

class BaseBase(object):
    """
    This class is a superclass of SA-generated Base class,
    which in turn is the superclass of all db-aware classes
    so we can define common functions here
    """

    def __setattr__(self, name, value):
        """
        Raise an exception if attempting to assign to an atribute which does not exist in the model.
        We're not checking if the attribute is an SQLAlchemy-mapped column because we also want it to work with properties etc.
        See http://stackoverflow.com/questions/12032260/ for more details.
        """ 
        if name != "_sa_instance_state" and not hasattr(self, name):
            raise AttributeError("Attribute %s is not a mapped column of object %s" % (name, self))
        super(BaseBase, self).__setattr__(name, value)

Base = declarative_base(cls=BaseBase)

Sort of "strict mode" for SQLAlchemy...