使用 MyPy 针对 TypedDict 验证 `Dict`

Question

我有几个数据处理器实现了一个接口，其方法“process”接管了处理部分，结果是 returned。结果应该是符合给定结构的字典。这就是我为每个处理器结果定义 TypedDict 的原因。也许我没有正确理解TypedDict，但我想实现这样的事情：

import abc

from typing import TypedDict

class AProcessorResult(TypedDict):
  param1: str
  param2: int

class BProcessorResult(TypedDict):
  paramA: str
  paramB: str
  paramC: float


class IProcessor(abc.ABC):

  def process(self) -> <Dictionary mypy-checked against processor result structure>:
    raise NotImplementedError


class AProcessor(IProcessor):

  def process(self) -> <Dictionary mypy-checked against AProcessorResult structure>:
    result: AProcessorResult = {
      'param1': 'value1',
      'param2': 0
    }
    return result


class BProcessor(IProcessor):

  def process(self) -> <Dictionary mypy-checked against BProcessorResult structure>:
    result: BProcessorResult = {
      'param1': 'value1',
      'param2': 1
    }
    return result


def main() -> None:

  aProcessor: AProcessor = AProcessor()
  aProcessor.process()                    # <- Should be successful during the MyPy check

  bProcessor: BProcessor = BProcessor()
  bProcessor.process()                    # <- Should fail during the MyPy check


if __name__ == '__main__':
  main()

如果我 return 来自“进程”方法的普通字典，MyPy 会抱怨类型不兼容：

Incompatible return value type (got "AProcessorResult", expected "Dict[Any, Any]")

此时我不想使用数据类，因为字典无论如何都会在后期进行“数据分类”，并且之前需要一些额外的字典处理。

有没有一种巧妙的方法以最抽象和通用的方式实现这一目标？

我正在使用 Python 3.8.

Answer 1

您可以使用泛型来实现这一点。基本上，您将 IProcess 定义为 return 一些通用类型，并定义它使用的具体类型 IProcessor[ConcreteType].

import abc

from typing import TypedDict, Any, Generic, TypeVar

T = TypeVar("T")


class AProcessorResult(TypedDict):
  param1: str
  param2: int

class BProcessorResult(TypedDict):
  paramA: str
  paramB: str
  paramC: float


class IProcessor(abc.ABC, Generic[T]):

  def process(self) -> T:
    raise NotImplementedError


class AProcessor(IProcessor[AProcessorResult]):

  def process(self) -> AProcessorResult:
    result: AProcessorResult = {
      'param1': 'value1',
      'param2': 0
    }
    return result


class BProcessor(IProcessor[BProcessorResult]):

  def process(self) -> BProcessorResult:
    result: BProcessorResult = {
      'param1': 'value1',
      'param2': 1
    }
    return result


def main() -> None:

  aProcessor: AProcessor = AProcessor()
  aProcessor.process()                    # <- Should be successful during the MyPy check

  bProcessor: BProcessor = BProcessor()
  bProcessor.process()                    # <- Should fail during the MyPy check


if __name__ == '__main__':
  main()

如果你想更严格并强制 return 类型始终是映射类型，你可以将类型 var 绑定为

Mapping
from typing import Mapping
T = TypeVar("T", bound=Mapping[str, Any])

您可以尝试使用这些解决方案here

使用 MyPy 针对 TypedDict 验证 `Dict`

Validate `Dict` against `TypedDict` with MyPy

python

type-hinting

mypy

typeddict