mypy - “Optional[CustomAttrsModel]”的項目“None”沒有屬性“country”

Question

當我運行 mypy 檢查時，出現錯誤。 我無法忽略它或將其關閉嚴格的可選檢查。 它有辦法解決這個問題。

這是引發錯誤的行：

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

其中attributes聲明為：

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

並且CustomAttrsModel聲明如下：

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

你能幫我解決這個問題嗎？

Answer 1

我不得不稍微調整一下你的片段以獲得 MWE，但我們開始吧：

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的，就使用assert something is not None ；）