Pydantic继承通用类

Question

我是 python 和 pydantic 的新手，有打字稿背景。我想知道你是否可以继承泛型类？

在打字稿中，代码如下所示

interface GenericInterface<T> {
  value: T
}

interface ExtendsGeneric<T> extends GenericInterface<T> {
  // inherit value from GenericInterface
  otherValue: string
}

const thing: ExtendsGeneric<Number> = {
  value: 1,
  otherValue: 'string'
}

我一直在尝试的是类似的东西

#python3.9
from pydantic.generics import GenericModel
from typing import TypeVar
from typing import Generic

T = TypeVar("T", int, str)

class GenericField(GenericModel, Generic[T]):
    value: T

class ExtendsGenericField(GenericField[T]):
    otherValue: str

ExtendsGenericField[int](value=1, otherValue="other value")

我得到了 TypeError: Too muchparameters for ExtendsGenericField; 的错误实际为 1，预期为 0。 这种检查是因为在 Pydantic 文档 中明确指出“为了声明通用模型...使用 TypeVar 实例作为注释，您将在其中替换它们...”简单的解决方法是使 ExtendsGeneric 继承于 GenericModel > 并且有value 在它自己的类定义中，但我试图重用类。

是否可以从泛型类继承值？

Answer 1

python中的仿制药有点奇怪，问题在于扩展了Sentenericfield本身并未将其声明为通用。要解决，只需添加generic [t]作为的超级类ExtendSgenericField：

from pydantic.generics import GenericModel
from typing import TypeVar
from typing import Generic

T = TypeVar("T", int, str)

class GenericField(GenericModel, Generic[T]):
    value: T

class ExtendsGenericField(GenericField[T], Generic[T]):
    otherValue: str

ExtendsGenericField[int](value=1, otherValue="other value")

Answer 2

不确定，但是转介您的我的代码工作:)

from datetime import datetime
from pydantic import BaseModel, parse_obj_as
from enum import Enum
import json
from typing import TypeVar, Generic
from pydantic.generics import GenericModel

class TradeOverlapping(BaseModel):
    COBDate: str
    DBServer: str

class EventType(Enum):
    STH_READY= 'STH_READY'

T = TypeVar("T")
class KafkaEvent(GenericModel,Generic[T]):
    Source: str
    Version: str
    TimeStamp: datetime
    Event: EventType
    Data: T

p = KafkaEvent[TradeOverlapping].parse_obj({"Source":"TOPIC","Version":"1.0","TimeStamp":"2022-08-03 06:49:17","Event":EventType('STH_READY'),"Data":TradeOverlapping(COBDate="2023-04-05", DBServer="DB_SERVER")})
print("Producer:")
print(p.json())

print("----------------------------")

value = '{"Source":"TOPIC","Version":"1.0","TimeStamp":"2022-08-03 06:49:17","Event":"STH_READY","Data":{"COBDate":"2023-04-05","DBServer":"DB_SERVER"}}'
obj = parse_obj_as(KafkaEvent[TradeOverlapping], json.loads(value))
print("Consumer:")
print(obj)

Answer 3

由于Pydantic V2（至少使用v2.6.x），因此以下作品（参考）：

# at least with Python 3.9
from typing import Generic, TypeVar
from pydantic import BaseModel

T = TypeVar("T")

class BaseClass(BaseModel, Generic[T]):
    value: T

class ChildClass(BaseClass[T], Generic[T]):
    other_value: str


x = ChildClass[int](value=1, other_value="other value")

type(x)
# __main__.ChildClass[int]