"Optional[CustomAttrsModel]"的项目"None"没有属性"country"

Question

当我运行mypy检查时，我得到一个错误。我无法忽略它或关闭严格的可选检查。有没有办法解决这个问题。

下面是抛出错误的那行:

if tree.data.attributes.custom != JAPAN:

其中attributes声明为:

class TreeAttributesModel(BaseModel):
id: Optional[TreeId]
name: Optional[str] = None
status: StatusEnum
custom: Optional[CustomAttrsModel] = None

和CustomAttrsModel的声明如下:

class CustomAttrsModel(BaseModel):
seller: Optional[str]
buyed_at: Optional[datetime]
country: Optional[Union[CountryEnum, str]]

你能帮我一下吗?

Answer 1

为了获得MWE，我不得不稍微调整一下代码片段，但现在我们开始:

import enum
import dataclasses
from datetime import datetime
from typing import Optional, Union

class StatusEnum(enum.Enum):
OK = enum.auto()
NOK = enum.auto()
class CountryEnum(enum.Enum):
JAPAN = enum.auto()
RAPTURE = enum.auto()
@dataclasses.dataclass
class TreeAttributesModel:
id: Optional[str]
name: Optional[str]  # = None had to remove default, attribs w/o default cannot follow attribs w/ one
status: StatusEnum
custom: Optional[CustomAttrsModel] = None

@dataclasses.dataclass
class CustomAttrsModel:
seller: Optional[str]
buyed_at: Optional[datetime]
country: Optional[Union[CountryEnum, str]]
custom = CustomAttrsModel(seller="test", buyed_at=None, country=CountryEnum.JAPAN)
attribs = TreeAttributesModel(id="test", name="test", status=StatusEnum.OK, custom=custom)
assert attribs.custom is not None  # this is typed as being optional, so make sure it isn't None
assert attribs.custom.country is not None  # same as above
result = attribs.custom.country != CountryEnum.JAPAN

消息是:只要something是Optional，就使用assert something is not None;)