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，但无法为ObjectId执行此操作

据我所知，我需要为ObjectId设置验证器，并尝试使用ObjectId扩展ObjectId类并将validator装饰器添加到我的类中。我这样做了。

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，这两个“解决方案”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。问题在于如何重写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才应该使用pydantic类型。Mongo将为您提供bsons。所以用真正的ObjectId实例化你的数据。所以data = {"who":ObjectId('123456781234567812345678')}是错误的，因为它使用了您的子类ObjectId。

Answer 2

另一种方法是使用pydantic，我从另一个来源发现它很有用，它是：

在models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，您可以在任何对象文件中使用它，如下面的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

这段代码帮助你使用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'}