Python - 实例方法中的多态性与静态方法中的多态性

Question

实例方法和静态方法之间有什么实际区别，因为这两个代码返回相同的结果？我知道静态方法不能对“self”进行操作，也不能直接访问属性，但是如何验证实例方法是否真正被重写（真正的多态性），而静态方法则不然？

class BaseClass:
    def instance_method(self):
        return "Instance method of base class"

    @staticmethod
    def static_method():
        return "Static method of base class"

class DerivedClass(BaseClass):
    def instance_method(self):
        return "Instance method of derived class"

    @staticmethod
    def static_method():
        return "Static method of derived class"

base_object = BaseClass()
derived_object = DerivedClass()

print(base_object.instance_method())  # Displays: "Instance method of base class"
print(derived_object.instance_method())  # Displays: "Instance method of derived class"

print(BaseClass.static_method())  # Displays: "Static method of base class"
print(DerivedClass.static_method())  # Displays: "Static method of derived class"

print(base_object.static_method())  # Displays: "Static method of base class"
print(derived_object.static_method())  # Displays: "Static method of derived class"

如何检查实例方法真正的多态性？也许我对多态性的整个概念理解错误？

Answer 1

与任何编程语言一样，您只需用该语言编写代码即可确定其行为：

class BaseClass:
    def instance_method(self):
        return "Instance method of base class"

    @staticmethod
    def static_method():
        return "Static method of base class"
    
    def normal_base_method(self):
        return self.static_method() + " called from normal_base_method"

class DerivedClass(BaseClass):
    def instance_method(self):
        return "Instance method of derived class"

    @staticmethod
    def static_method():
        return "Static method of derived class"

base_object = BaseClass()
derived_object = DerivedClass()

print(base_object.normal_base_method())
print(derived_object.normal_base_method())

输出：

Static method of base class called from normal_base_method
Static method of derived class called from normal_base_method

上面的输出显示，调用仅在基类中定义的方法会更改行为，因为该实例属于派生类。

调用

derived_object.normal_base_method()

确实调用了

BaseClass.normal_base_method

，但是因为

self

引用了

derived_object

，所以

static_method

是从

DerivedClass

中选择的。