How to discover table properties from SQLAlchemy mapped object

Question

I have a class mapped with a table, in my case in a declarative way, and I want to “discover” table properties, columns, names, relations, from this class:

engine = create_engine('sqlite:///' + databasePath, echo=True)

# setting up root class for declarative declaration
Base = declarative_base(bind=engine)

class Ship(Base):
    __tablename__ = 'ships'

    id = Column(Integer, primary_key=True)
    name = Column(String(255))

    def __init__(self, name):
            self.name = name

    def __repr__(self):
            return "<Ship('%s')>" % (self.name)

So now my goal is from the “Ship” class to get the table columns and their properties from another piece of code. I guess I can deal with it using instrumentation but is there any way provided by the SQLAlchemy API?

Asked By: Olivier Girardot

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Source

Answer 1

Information you need you can get from Table object:

Ship.__table__.columns will provide you with columns information
Ship.__table__.foreign_keys will list foreign keys
Ship.__table__.constraints, Ship.__table__.indexes are other properties you might find useful

Answered By: van

Answer 2

If declarative base is not used, the answer fails. The following should work no matter how it’s initialized

For Class Object:

TableClass.sa_class_manager.mapper.mapped_table.name

For Instance Object:

tableObj.sa_instance_state.mapper.mapped_table.name

Answered By: Hamza Zubair

How to discover table properties from SQLAlchemy mapped object

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