Python Generic generation from typevar Python 3.9.5 tested

generics.py

from abc import abstractmethod
from typing import TypeVar, Generic, get_args, Type, List


class Fruit:
    @abstractmethod
    def fruit_name(self) -> str:
        raise NotImplementedError


class Apple(Fruit):
    def fruit_name(self) -> str:
        return self.__class__.__name__


class Leaf:
    @staticmethod
    def leaf_color():
        return "green"


_FruitType = TypeVar("_FruitType", bound=Fruit)


class Tree(Generic[_FruitType], Leaf):
    _type_generic: Type[_FruitType]
    _fruits: List[_FruitType]
        
    def __init__(self) -> None:
        super().__init__()
        self._type_generic = get_args(self.__orig_bases__[0])[0] # magic here idea from https://stackoverflow.com/a/71720366/481637
        self._fruits = list()

    def generate_fruit(self):
        self._fruits.append(self._type_generic())

    def take_fruit(self) -> _FruitType:
        if not self._fruits:
            raise NotImplementedError

        return self._fruits.pop()

    @property
    def count_fruits(self) -> int:
        return len(self._fruits)

    def tree_name(self):
        return self.__class__.__name__


class Fuji(Tree[Apple]):
    pass


class Person:
    @staticmethod
    def eat(food: Fruit):
        print(f"eating {food.fruit_name()} ñam")
        food = None


fuji_apple_tree = Fuji()
print(f"Created {fuji_apple_tree.tree_name()} Tree with {fuji_apple_tree.leaf_color()} color")
# Created Fuji Tree with green color

fuji_apple_tree.generate_fruit()
print(f"{fuji_apple_tree.tree_name()} Tree with {fuji_apple_tree.count_fruits} fruits generated")
# Fuji Tree with 1 fruits generated


fruit = fuji_apple_tree.take_fruit()
person = Person()
person.eat(fruit)
# eating Apple ñam

without_generics.py

from abc import abstractmethod
from typing import Type, List


class Fruit:
    @abstractmethod
    def fruit_name(self) -> str:
        raise NotImplementedError


class Apple(Fruit):
    def fruit_name(self) -> str:
        return self.__class__.__name__


class Leaf:
    @staticmethod
    def leaf_color():
        return "green"


class Tree(Leaf):
    _fruits: List[Fruit]

    @property
    @abstractmethod
    def kind_of_fruit(self) -> Type[Fruit]:
        raise NotImplementedError

    def __init__(self) -> None:
        super().__init__()
        self._fruits = list()

    def generate_fruit(self):
        self._fruits.append(self.kind_of_fruit())

    def take_fruit(self) -> Fruit:
        if not self._fruits:
            raise IndexError

        return self._fruits.pop()

    @property
    def count_fruits(self) -> int:
        return len(self._fruits)

    def tree_name(self):
        return self.__class__.__name__


class Fuji(Tree):
    @property
    def kind_of_fruit(self) -> Type[Apple]:
        return Apple


class Person:
    @staticmethod
    def eat(food: Fruit):
        print(f"eating {food.fruit_name()} ñam")
        food = None


fuji_apple_tree = Fuji()
print(f"Created {fuji_apple_tree.tree_name()} Tree with {fuji_apple_tree.leaf_color()} color")

fuji_apple_tree.generate_fruit()
print(f"{fuji_apple_tree.tree_name()} Tree with {fuji_apple_tree.count_fruits} fruits generated")
fruit = fuji_apple_tree.take_fruit()
fruit.fruit_name()
person = Person()
person.eat(fruit)