Python / Django-Mypy：表达式的类型为“ Type [ModelInstance]”，变量的类型为“ ModelInstance”

Question

我正在开发一个为前端提供GraphQL api的Django应用。我正在使用mypy进行类型检查，并且在运行mypy时遇到了我不理解的错误

运行时出现以下错误：

api/schema.py:50: error: Incompatible types in assignment (expression has type "Type[Academy]", variable has type "Academy")
api/schema.py:57: error: Incompatible types in assignment (expression has type "Type[School]", variable has type "School")
api/schema.py:64: error: Incompatible types in assignment (expression has type "Type[AcademyGroup]", variable has type "AcademyGroup")

这是mypy正在检查的代码

class AcademyType(DjangoObjectType):
    class Meta:
        model: Academy = Academy
        filter_fields: List[str] = ['name', 'domain', 'slug']
        interfaces: Tuple = (relay.Node,)


class SchoolType(DjangoObjectType):
    class Meta:
        model: School = School
        filter_fields: List[str] = ['name', 'academy']
        interfaces: Tuple = (relay.Node,)


class AcademyGroupType(DjangoObjectType):
    class Meta:
        model: AcademyGroup = AcademyGroup
        filter_fields: List[str] = ['name', 'academy']
        interfaces: Tuple = (relay.Node,)

所以一直失败的行是model: AcademyGroup = AcademyGroup的变体，但这只是在我的代码中不断发生的'Django模型为类型'定义（似乎并没有产生错误）

因此，我不太确定自己在这里做错了什么，因此将不胜感激。

Answer 1

model属性的类型不是类本身，而是Type。确实，如果您说model = Academy，则model的类型是type(model) == type(Academy) == Type，的确，Academy是not和Academy object，它是对类的引用，此类的类型是Type的（子类）。您还可以使用Type[…] [python-doc]指定类型的（base-）类，因此Type[…]表示它是Type[C]的类型，或者是C的子类：

因此，您应将其注释为：

C