underscore_attrs_are_private cannot use

[dongfengweixiao]

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• I already checked if it is not related to SQLModel but to Pydantic.
• I already checked if it is not related to SQLModel but to SQLAlchemy.

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Example Code

from sqlmodel import SQLModel


class UserBase(SQLModel):
    first_name: str
    last_name: str


class UserSchema(UserBase):
    class Config:
        underscore_attrs_are_private = True


if __name__ == "__main__":
    print("Hello world!")

Description

File "c:\Users\dongf\Source\Python\test\main.py", line 9, in
class UserSchema(UserBase):
File "C:\Users\dongf\Source\Python\test\venv\Lib\site-packages\sqlmodel\main.py", line 272, in new
new_cls = super().new(cls, name, bases, dict_used, **config_kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "pydantic\main.py", line 283, in pydantic.main.ModelMetaclass.new
File "", line 106, in new
TypeError: weakref slot disallowed: either we already got one, or itemsize != 0

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.8

Python Version

Python 3.11.0, Python 3.9.0

Additional Context

No response

[meirdev]

The reason for the problem is because of this line:

https://github.com/tiangolo/sqlmodel/blob/5fa9062ed94b2be090ef9d15ea6666d347d1a2a6/sqlmodel/main.py#L253

We need to remove __weakref__ from dict_used to make it work:

dict_used.pop("__weakref__", None)

But it is not easy to do this without changing the sqlmodel code.

Based on #472 you can do something like this:

from sqlmodel import SQLModel, Field, create_engine, Session, select
from typing import Optional, Any
from pydantic import PrivateAttr


class PatchSQLModel(SQLModel):
    def __init__(__pydantic_self__, **data: Any) -> None:
        super(PatchSQLModel, __pydantic_self__).__init__(**data)
        __pydantic_self__._init_private_attributes()


class UserBase(PatchSQLModel):
    id: Optional[int] = Field(default=None, primary_key=True)
    first_name: str
    last_name: str
    _private: int = PrivateAttr(default="my_private_attribute")


class UserSchema(UserBase, table=True):
    pass


engine = create_engine("sqlite:///:memory:")

with Session(engine) as session:
    SQLModel.metadata.create_all(engine)

    user = UserSchema(first_name="john", last_name="Doe", _private="not cahnged")

    print(user._private)  # my_private_attribute

    session.add(user)
    session.commit()

    statement = select(UserSchema)
    user = session.exec(statement).first()

    print(user, user._private)  # first_name='john' last_name='Doe' id=1 my_private_attribute