[Python] "Type Error: argument of type 'method' is not iterabe" while initializing SQLAlchemy...

I have a SQLAlchemy ORM with SqlAlchemy 2.0 using mapped_column() and Deklarative Base. My App starts with falcon and gunicorn in my PyCharm venv with Python3.12.

The database tables are created correctly with:

models.Base.metadata.create_all(self.engine)


I have a Postgres database and all tables with their columns are created correctly, also manually creating an entry is working fine.

But creating an entry using SQLAlchemy Object init fails, with an error I don't understand.

from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship

class Base(DeclarativeBase):
pass

class VirtualMachine(Base):
__tablename__ = "virtual_machine"

vm_id: Mapped[int] = mapped_column(primary_key=True)
object_name: Mapped[str] = mapped_column()

def __init__(self, object_name: str):
self.vm_id = 1
self.object_name = object_name

def __repr__(self):
pass

def __dict__(self):
pass


It's not my first time using SQLAlchemy ORM for database management, but I don't have a clue what this error message means while trying to create an object 'VirtualMachine' in my unit tests.

class TestVM(unittest.TestCase):
def setUp(self):
self.data = {
"object_name": "test-vm"
}
engine = sqlalchemy.create_engine(connect_str)
self.db = engine.connect()

def test_create_vm(self):
self.test_vm = VirtualMachine(**self.data)

Error
Traceback (most recent call last):
File "/api/tests/orm_test/vm_object_test.py", line 51, in test_create_vm
self.test_vm = VirtualMachine(**self.data)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "", line 4, in init
File "/api/venv/lib64/python3.12/site-packages/sqlalchemy/orm/state.py", line 571, in initialize_instance
with util.safe_reraise():
File "/api/venv/lib64/python3.12/site-packages/sqlalchemy/util/langhelpers.py", line 146, in exit
raise exc_value.with_traceback(exc_tb)
File "/api/venv/lib64/python3.12/site-packages/sqlalchemy/orm/state.py", line 569, in initialize_instance
manager.original_init(*mixed[1:], **kwargs)
File "/api/src/database/models.py", line 58, in init
self.vm_id = 1
^^^^^^^^^^
File "/api/venv/lib64/python3.12/site-packages/sqlalchemy/orm/attributes.py", line 537, in set
self.impl.set(
File "/api/venv/lib64/python3.12/site-packages/sqlalchemy/orm/attributes.py", line 1272, in set
old = self.get(state, dict, PASSIVE_RETURN_NO_VALUE)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "api/venv/lib64/python3.12/site-packages/sqlalchemy/orm/attributes.py", line 1074, in get
if self.key in dict:
^^^^^^^^^^^^^^^^^

TypeError: argument of type 'method' is not iterable
​

Does anyone have any idea why it can't be initialized correctly?

I also tried with other data types, because in the beginning, I had uuid.UUID as Mapped[type], and I had asyncio integrated which I now keep out everywhere and started a wsgi app now.

I thought it might be a problem with the session, but I think it isn't.

Continue reading...