I believe my problem is related to https://bitbucket.org/zzzeek/sqlalchemy/issues/4124.
I have an AbstractConcreteBase inheritance hierarchy that looks like this: class AbstractBase(AbstractConcreteBase, Base): @declared_attr def column1(cls): return Column(...) @declared_attr def column2(cls): return Column(...) class Concrete1(AbstractBase): __tablename__ = "concrete1" attribute1 = Column(...) __mapper_args__ = { 'polymorphic_identity': 'concrete1', 'concrete': True } class Concrete2(AbstractBase): __tablename__ = "concrete2" @hybrid_property def attribute1(self): return ... @attribute1.expression def attribute1(cls): return ... __mapper_args__ = { 'polymorphic_identity': 'concrete2', 'concrete': True } Then, if I refer to `attribute1` on an instance if Concrete2, I get an AttributeError: ... File "/home/charles/PycharmProjects/MyProject/models/setup/model.py", line 350, in generate_seasonality x = concrete2_instance.attribute1 File "/home/charles/PycharmProjects/Konversion_Platform-Back-End/.env/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 298, in __get__ return self.descriptor.__get__(instance, owner) File "/home/charles/PycharmProjects/Konversion_Platform-Back-End/.env/lib/python3.6/site-packages/sqlalchemy/orm/descriptor_props.py", line 512, in __get__ warn() File "/home/charles/PycharmProjects/Konversion_Platform-Back-End/.env/lib/python3.6/site-packages/sqlalchemy/orm/descriptor_props.py", line 500, in warn (self.parent, self.key, self.parent)) AttributeError: Concrete Mapper|Concrete2|concrete2 does not implement attribute 'attribute1' at the instance level. Add this property explicitly to Mapper|Concrete2|concrete2. I'm running SQLAlchemy 1.2.2. If the problem is indeed the same as in https://bitbucket.org/zzzeek/sqlalchemy/issues/4124 , then I believe it was supposed to have been fixed in 1.2.0. Thanks for any help! -- 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 post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.