如何在 pydantic 模型中解析 ObjectId？

Question

我正在尝试将 MongoDB 记录解析为 pydantic 模型，但未能为 ObjectId

解析

据我了解，我需要为 ObjectId 设置验证器，并尝试使用 ObjectId 扩展 ObjectId class 并将 validator 装饰器添加到我的 class。我做了如下。

from pydantic import BaseModel, validator
from bson.objectid import ObjectId


class ObjectId(ObjectId):
    pass
    @classmethod
    def __get_validators__(cls):
        yield cls.validate
    @classmethod
    def validate(cls, v):
        if not isinstance(v, ObjectId):
            raise TypeError('ObjectId required')
        return str(v)


class User(BaseModel):
    who: ObjectId


class User1(BaseModel):
    who: ObjectId
    @validator('who')
    def validate(cls, v):
        if not isinstance(v, ObjectId):
            raise TypeError('ObjectId required')
        return str(v)

data = {"who":ObjectId('123456781234567812345678')}

不幸的是，"solution" 都失败了，如下所示：

>>> test = User(**data)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pydantic/main.py", line 274, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for User
id
  field required (type=value_error.missing)

>>> test = User1(**data)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pydantic/main.py", line 274, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for User1
who
  ObjectId required (type=type_error)

这里肯定有我遗漏的东西。

Answer 1

您的第一个测试用例运行良好。问题在于你如何覆盖 ObjectId.

from pydantic import BaseModel
from bson.objectid import ObjectId as BsonObjectId


class PydanticObjectId(BsonObjectId):
    @classmethod
    def __get_validators__(cls):
        yield cls.validate

    @classmethod
    def validate(cls, v):
        if not isinstance(v, BsonObjectId):
            raise TypeError('ObjectId required')
        return str(v)


class User(BaseModel):
    who: PydanticObjectId


print(User(who=BsonObjectId('123456781234567812345678')))

打印

who='123456781234567812345678'

只有 pydantic 应该使用 pydantic 类型。 Mongo 将为您提供 bsons ObjectId。所以用真实的 ObjectId 实例化你的数据。所以 data = {"who":ObjectId('123456781234567812345678')} 是错误的，因为它使用了您的 child ObjectId class.

Answer 2

另一种方法是使用 pydantic，我从另一个来源发现它很有用：

在模型文件夹中定义一个名为 PyObjectId.py 的文件。

from pydantic import BaseModel, Field as PydanticField
from bson import ObjectId

class PyObjectId(ObjectId):
    @classmethod
    def __get_validators__(cls):
        yield cls.validate
    @classmethod
    def validate(cls, v):
        if not ObjectId.is_valid(v):
            raise ValueError("Invalid objectid")
        return ObjectId(v)
    @classmethod
    def __modify_schema__(cls, field_schema):
        field_schema.update(type="string")

然后你可以像这样在你的任何目标文件中使用它 users.py

from models.PyObjectId import PyObjectId
from pydantic import BaseModel, Field as PydanticField
from bson import ObjectId
class Users(BaseModel):
    id: PyObjectId = PydanticField(default_factory=PyObjectId, alias="_id")
    class Config:
        allow_population_by_field_name = True
        arbitrary_types_allowed = True #required for the _id 
        json_encoders = {ObjectId: str}

Answer 3

开始使用 MongoDB 和 FastAPI

Mongo Developers

此代码可帮助您使用 json 编码器

from bson import ObjectId
from pydantic import BaseModel


class ObjId(ObjectId):
    @classmethod
    def __get_validators__(cls):
        yield cls.validate

@classmethod
def validate(cls, v: str):
    try:
        return cls(v)
    except InvalidId:
        raise ValueError("Not a valid ObjectId")


class Foo(BaseModel):
    object_id_field: ObjId = None

    class Config:
        json_encoders = {
            ObjId: lambda v: str(v),
        }



obj = Foo(object_id_field="60cd778664dc9f75f4aadec8")
print(obj.dict())
# {'object_id_field': ObjectId('60cd778664dc9f75f4aadec8')}
print(obj.json())
# {'object_id_field': '60cd778664dc9f75f4aadec8'}

如何在 pydantic 模型中解析 ObjectId？

How to parse ObjectId in a pydantic model?

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mongodb

parsing

objectid

pydantic