用SQLAlchemy和mypy定义的模型在初始化期间需要一个关系参数。

huangapple
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英文:

Model defined with SQLAlchemy and mypy requires a relationship parameter during initialization

问题

以下是代码的翻译部分，不包括代码本身：

  1. 我定义了如下模型：
  3. class Base(MappedAsDataclass, DeclarativeBase):
  4.     """子类将被转换为数据类"""
  6. class Prompt(Base):
  7.     __tablename__ = "Prompt"
  9.     id = mapped_column(
  10.         "id",
  11.         UUID(as_uuid=True),
  12.         primary_key=True,
  13.         index=True,
  14.         server_default=sa.text("gen_random_uuid()"),
  15.     )
  16.     created_at = mapped_column(
  17.         "created_at", DateTime(timezone=True), server_default=func.now(), nullable=False
  18.     )
  19.     text: Mapped[str] = mapped_column(Text)
  20.     display_name: Mapped[str] = mapped_column("display_name", String)
  22.     # 一对多关系
  23.     owner_id: Mapped[uuid.UUID] = mapped_column(
  24.         "owner_id",
  25.         UUID(as_uuid=True),
  26.         ForeignKey("User.id"),
  27.     )
  29.     owner: Mapped[User] = relationship("User", back_populates="prompts")
  31.     # 多对多关系
  32.     transcripts: Mapped[List[Transcript]] = relationship(
  33.         "Transcript",
  34.         secondary=transcript_prompt_association,
  35.         back_populates="prompts",
  36.     )
  38.     deleted: Mapped[bool] = mapped_column("deleted", Boolean, default=False)

当我想要创建模型的实例时：

  1. db_prompt = models.Prompt(text=text, display_name=display_name, owner_id=user_id)

我收到以下错误信息：

  1. 在调用“Prompt”时缺少位置参数“owner”和“transcripts” [call-arg]mypy

我应该如何修复它？

我已经尝试过：

  1. owner: Optional[Mapped[User]] = relationship("User", back_populates="prompts")

=> 同样的错误。

我认为mypy应该自动理解在初始化时不需要关系字段。

编辑：

我的mypy.ini

  1. [mypy]
  2. python_version = 3.11
  3. plugins = pydantic.mypy,sqlalchemy.ext.mypy.plugin
  4. ignore_missing_imports = True
  5. disallow_untyped_defs = True
  6. exclude = (?x)(
  7.     alembic    # 文件名为“one.py”
  8. )
英文:

I have a model defined as following:

  1. class Base(MappedAsDataclass, DeclarativeBase):
  2.     """subclasses will be converted to dataclasses"""
  5. class Prompt(Base):
  6.     __tablename__ = "Prompt"
  8.     id = mapped_column(
  9.         "id",
  10.         UUID(as_uuid=True),
  11.         primary_key=True,
  12.         index=True,
  13.         server_default=sa.text("gen_random_uuid()"),
  14.     )
  15.     created_at = mapped_column(
  16.         "created_at", DateTime(timezone=True), server_default=func.now(), nullable=False
  17.     )
  18.     text: Mapped[str] = mapped_column(Text)
  19.     display_name: Mapped[str] = mapped_column("display_name", String)
  21.     # many to one relationship
  22.     owner_id: Mapped[uuid.UUID] = mapped_column(
  23.         "owner_id",
  24.         UUID(as_uuid=True),
  25.         ForeignKey("User.id"),
  26.     )
  28.     owner: Mapped[User] = relationship("User", back_populates="prompts")
  30.     # many-to-many relationship
  31.     transcripts: Mapped[List[Transcript]] = relationship(
  32.         "Transcript",
  33.         secondary=transcript_prompt_association,
  34.         back_populates="prompts",
  35.     )
  37.     deleted: Mapped[bool] = mapped_column("deleted", Boolean, default=False)

When I want to create an instance of the model:

  1. db_prompt = models.Prompt(text=text, display_name=display_name, owner_id=user_id)

I receive the following error:

  1. Missing positional arguments "owner", "transcripts" in call to "Prompt"  [call-arg]mypy

How can I fix it?

I already tried to:

  1. owner: Optional[Mapped[User]] = relationship("User", back_populates="prompts")

=> Same error.

I thought mypy understands automatically that a relationship field is not required during init.

EDIT:

My mypy.ini

  1. [mypy]
  2. python_version = 3.11
  3. plugins = pydantic.mypy,sqlalchemy.ext.mypy.plugin
  4. ignore_missing_imports = True
  5. disallow_untyped_defs = True
  6. exclude = (?x)(
  7.     alembic    # files named "one.py"
  8.   )

答案1

得分: 1

由于您的Base扩展了MappedAsDataClass，所以您在这里使用了一个Python数据类。错误消息“缺少位置参数“owner”…”来自于生成的初始化方法中，“owner”是一个必需的字段（mypy只是提醒您这一点）。

您可以通过添加init=False来将owner从必需字段中排除：

  1. owner: Mapped[User] = relationship("User", back_populates="prompts", init=False)

或者，您可以为其提供默认值None：

  1. owner: Mapped[User] = relationship("User", back_populates="prompts", default=None)

然而，如果您给它一个默认值为None，并且仍然使用之前的方法初始化实例：

  1. db_prompt = models.Prompt(text=text, display_name=display_name, owner_id=user_id)

owner字段将由于数据类生成初始化方法的方式而覆盖owner_id为None。

因此，您可以选择：

  1. 不要使用数据类为此类自动生成初始化方法：
  1. class Prompt(Base, init=False):
  1. 或者，添加一个后初始化方法，如果它是None，则删除该属性，以便您的owner_id不会被空值覆盖：
  1. def __post_init__(self):
  2.     if (self.owner is None):
  3.         delattr(self, "owner")

这是一种有点巧妙的方法，不建议使用。在您进行修改后，您可以使用Prompt(owner_id=user_id, ...或Prompt(owner=user...来实例化一个实例。

英文:

Since your Base extends MappedAsDataClass, you are using a Python dataclass
here. The error message "Missing positional arguments "owner", ..." comes from
the fact that in the generated init method, "owner" is a required field (mypy is
just reminding you of that fact).

You can exclude owner from the required field by adding init=False:

  1. owner: Mapped[User] = relationship("User", back_populates="prompts", init=False)

Alternatively, you can give it a default value of None:

  1. owner: Mapped[User] = relationship("User", back_populates="prompts", default=None)

However, if you give it a default value of None and still use your previous
method to initialize the instance:

  1. db_prompt = models.Prompt(text=text, display_name=display_name, owner_id=user_id)

The owner field will overwrite owner_id with None due to how a dataclass
generates the init method.

So, you can either:

  1. Don't use dataclass to automatically generate the init method for this class:
  1. class Prompt(Base, init=False):
  1. Or, add a post init method and remove the the attribute if it's None so
    your owner_id does not get overwritten by a null value:
  1. def __post_init__(self):
  2.     if (self.owner is None):
  3.         delattr(self, "owner")

This is kind of a hack and is not recommended. After you made the modification,
you can instantiate an instance with either Prompt(owner_id=user_id, ... or
Prompt(owner=user....

huangapple
  • 本文由 发表于 2023年6月2日 08:13:36
  • 转载请务必保留本文链接：https://go.coder-hub.com/76386442.html
  • mypy
  • python
  • sqlalchemy
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