Python-day15

1、动态语言

class animal:
    def eat(self):
        print('animal will eat')
class dog(animal):
    def eat(self):
        print('dog is eating bone')
class cat(animal):
    def eat(self):
        print('cat is eating fish')
class person:
    def eat(self):
        print('people is eating corn')
def fun(obj):
    obj.eat()
fun(animal)
fun(dog())
fun(cat())
fun(person())

2、特殊属性和特殊方法

class A:
    pass
class B:
    pass
class C(A,B):
    def __init__(self,name,age):
        self.name=name
        self.age=age
x=C('cecilia',1)
print(x.__dict__)
print(C.__dict__)
print(x.__class__)
print(C.__bases__)
print(C.__base__)
print(C.__mro__)
print(A.__subclasses__())

class Student:
    def __init__(self,name):
        self.name=name
    def __add__(self,other):
        return self.name+other.name
    def __len__(self):
        return len(self.name)
stu1=Student('Ann')
stu2=Student('Jack')
print(stu1+stu2)
s=stu1.__add__(stu2)
print(s)
print(len(stu1))