python 3.8 中的 singledispatchmethod 和类方法装饰器

Python 3.8新特性：singledispatchmethod和类方法装饰器

python
from functools import singledispatchmethod
class Shape:
    @singledispatchmethod
    def draw(self, shape):
        raise NotImplementedError('Cannot draw the shape')
    
    @draw.register
    def _(self, shape: 'Circle'):
        print('Drawing a circle')
    
    @draw.register
    def _(self, shape: 'Rectangle'):
        print('Drawing a rectangle')
        
class Circle(Shape):
    pass
class Rectangle(Shape):
    pass
shape1 = Circle()
shape2 = Rectangle()
shape1.draw(shape1)  # 输出：Drawing a circle
shape2.draw(shape2)  # 输出：Drawing a rectangle

python
class Person:
    age = 25
    
    @classmethod
    def get_age(cls):
        return cls.age
    
class Student(Person):
    age = 20
    
print(Person.get_age())  # 输出：25
print(Student.get_age())  # 输出：20