SQLModel: sqlalchemy.exc.ArgumentError: Column expression or FROM clause expected,

Question

I am using the SQLModel library to do a simple select() like described on their official website. However I am getting Column expression or FROM clause expected error message

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select

from models import Hero
    
sqrl = f"mysql+pymysql:///roo@asdf:localhost:3306/datab"

engine = create_engine(sqrl, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def select_heroes():
    with Session(engine) as session:
        statement = select(Hero)
        results = session.exec(statement)
        for hero in results:
            print(hero)


def main():
    select_heroes()


if __name__ == "__main__":
    main()

this is my models/Hero.py code:

from datetime import datetime, date, time
from typing import Optional
from sqlmodel import Field, SQLModel

class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str
    secret_name: str
    age: Optional[int] = None
    created: datetime
    lastseen: time

when I run app.py I get the sqlalchemy.exc.ArgumentError: Column expression or FROM clause expected, got . message

user_5320906 · Answer

The error message tells us:

SQLModel / SQLAlchemy unexpectedly received a module object named models.Hero
that you have a module named Hero.py

The import statement from models import Hero only imports the module Hero. Either

change the import to import the model^*
```
from models.Hero import Hero
```
change the code in select_heroes to reference the model^†
```
statement = select(Hero.Hero)
```

* It's conventional to use all lowercase for module names; following this convention will help you distinguish between modules and models.

† This approach is preferable in my opinion: accessing the object via the module namespace eliminates the possibility of name collisions (of course it can be combined with lowercase module names).

SQLModel: sqlalchemy.exc.ArgumentError: Column expression or FROM clause expected,

1 Answers