在python中将实例类型更改为继承 [英] Change instance type to inheritance in python

问题描述

我有一个类 Person 和两个类 Child 和 Adult 继承自 `Person.

<预><代码>班级人物:def __init__(self, name):self.name = 姓名self.age = 0def say_hi(self):print("我是" + self.name)def set_age(self, age):self.age = 年龄班级儿童(人):def play_with_children(self):打印(和孩子们一起玩")班级成人(人):def Drink_alcohol(自我):打印(喝")

我想从 Person 创建一个实例 然后 设置它的 age 并且根据它这个实例应该成为"一个 儿童或成人.

另外，如果它是一个 Child 并且它的 age 增加，我希望它成为"一个 Adult.请注意，此代码有一个错误，因为 Person 的构造函数需要一个 name，因为它旨在创建一个新实例.

person1 = Person("Marvin")person1.set_age(15)如果 person1.age <21:person1 = Child()# 这是一个错误 =>期待名字#但我不想像这样处理所有成员=>person1 = Child(person1.name)#我不想要一个新实例，这可能吗?person1.say_hi()person1.play_with_children()person1.set_age(25)如果 person1.age >21:person1 = Adult()# 这是一个错误 =>期待名字#但我不想像这样处理所有成员=>person1 = 成人(person1.name)#我不想要一个新实例，这可能吗?person1.say_hi()person1.drink_alcohol()

• 这可能吗?

• 这可以在不创建新实例的情况下完成吗?

PS:这只是一个示例代码，显示了我遇到的一个更复杂的问题(不是真正的儿童和成人:D).

解决方案

正如评论中提到的，在 Python 3 中，我们可以访问任何实例的 __class__ 并对其进行更改.

虽然你必须小心，但你可以将多个类的属性添加到同一个实例并创建一个奇怪的怪物(方法是安全的).

person1 = Person("Marvin")person1.set_age(15)如果 person1.age <21:person1.__class__ = 孩子person1.say_hi()person1.play_with_children()person1.set_age(25)如果 person1.age >21:person1.__class__ = 成人person1.say_hi()person1.drink_alcohol()

所以怪物:

类狗:def wouf(自我):打印(wouf")person1.__class__ = 狗print("属性已保存，名称:"+ person1.name)#但是方法不行，所以现在我不能使用person1.say_hi()person1.wouf()

I have a class Person and 2 classes Child and Adult that inherit from `Person.

class Person:

    def __init__(self, name):
        self.name = name
        self.age = 0

    def say_hi(self):
        print("Hi, I am " + self.name)

    def set_age(self, age):
        self.age = age

class Child(Person):

    def play_with_children(self):
        print("Playing with children")

class Adult(Person):

    def drink_alcohol(self):
        print("drinking")

I want to create an instance from Person then set it's age and according to it this instance should "become" a Child or an Adult.

Also if it's a Child and it's age increases I'd like it to "become" an Adult. Note that this code has an error because the Person's constructor expects a name because it's meant to create a new instance.

person1 = Person("Marvin")

person1.set_age(15)

if person1.age < 21:
    person1 = Child()# This is an error => expects the name
    #But I wouldn't like to handle all members like this => person1 = Child(person1.name)
    #I don't want a new instance, is that even posible?

person1.say_hi() 
person1.play_with_children()


person1.set_age(25)

if person1.age > 21:
    person1 = Adult()# This is an error => expects the name
    #But I wouldn't like to handle all members like this => person1 = Adult(person1.name)
    #I don't want a new instance, is that even posible?

person1.say_hi()   
person1.drink_alcohol()

• Is this even possible?

• Can this be done without creating new instances?

PS: this is just a sample code showing the problem from a more complex problem that I have (Not really children and adults :D ).

解决方案

As mentioned in the comments, in Python 3 we can access the __class__ of any instance and change it.

Although you must be careful, with this you can add attributes of several classes to the same instance and create a weird monster (methods are safe).

person1 = Person("Marvin")

person1.set_age(15)

if person1.age < 21:
    person1.__class__ = Child

person1.say_hi() 
person1.play_with_children()


person1.set_age(25)

if person1.age > 21:
    person1.__class__ = Adult


person1.say_hi()   
person1.drink_alcohol()

So the monster:

class Dog:

    def wouf(self):
        print("wouf")

person1.__class__ = Dog
print("Attributes are saved, name: "+ person1.name)
#But methods not, so now I can't use person1.say_hi()
person1.wouf()

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