import abc
from typing import ClassVar

from pydantic import BaseModel
from devtools import debug

class Fruit(BaseModel, abc.ABC):
    @property
    @abc.abstractmethod
    def type(self) -> str:
        """The name of the type of fruit."""

class Apple(Fruit):
    type: ClassVar[str] = "apple"
    size: int

a = Apple(size=4)
debug(a, a.type)

Unless you want to allow type to be changed when creating a model instance, in which case just make it a field on Fruit.

Since Python 3.3 a bug was fixed meaning the property() decorator is now correctly identified as abstract when applied to an abstract method.

Note: Order matters, you have to use @property above @abstractmethod

Python 3.3+: (python docs):

from abc import ABC, abstractmethod

class C(ABC):
    @property
    @abstractmethod
    def my_abstract_property(self):
        ...

Python 2: (python docs)

from abc import ABCMeta, abstractproperty

class C:
    __metaclass__ = ABCMeta

    @abstractproperty
    def my_abstract_property(self):
        ...

After some thought, I think the second code snippet does not use the Factory method as it is not concerned with the creation of objects.

However, the code can be refactored to use the Factory method and better communicate the intent:

class CraneInterface(ABC):

    def __init__(self):
        self.__axis = self._make_axis()

    @property
    def axis(self) -> AxisInterface:
        return self.__axis

    @abstractmethod
    def _make_axis(self) -> AxisInterface:
        """
        Factory method: "Subclasses override to change the class of object that will be created"
        """
        pass