python高级类与对象深度

1.   abc模块 ，不要以abc为模块名称

class Demo(object):
    def __init__(self, li):
        self.li = li
    def __len__(self):
        return len(self.li)
l = ['c', '李云', '九折']
d = Demo(l)
print(d)  # <__main__.Demo object at 0x00000218C9347160>
print(len(d))   # 会触发__len__    返回 3
如何判断Demo中是否含有 __len__魔法方法
print(hasattr(d,'__len__')) # 判断d的内部是否含有__len__  返回为bool

2.第一种方法实现：子类重写父类的方法，

class CacheBase(object):
    def dele(self):
        raise NotImplementedError
    def crea(self):
        raise NotImplementedError
class RedisBase(CacheBase):
    """
    1. 子类 如果不重写 父类的方法，访问时，就会报错
    """
    def crea(self):
        print('hahah')
r = RedisBase()
主动抛出异常：调用时才会检测
r.crea()
r.dele()
r.crea()
3.第二种方法实现：子类重写父类的方法，

import abc
# 注意：不直接继承object 而是继承abc.ABCMeta
class CacheBase(metaclass=abc.ABCMeta):
    @abc.abstractmethod
    def dele(self):
        pass
    @abc.abstractmethod
    def crea(self):
        pass
class RedisBase(CacheBase):
    def dele(self):
        pass
    def crea(self):
        pass
# r = RedisBase()
# r.crea()
# r.dele()

# 抽象基类：实例化的时候检测
# 主动抛出异常：调用时才会检测

4.type 和isinstance()的区别

a = 1
b = '23'
print(isinstance(b,(int,str)))  # 返回bool类型  （）元组类型----or运算
print(type(a))                  #  <class 'int'>

class Father(object):
    pass
class Son(Father):
    pass
ls = Son()
# print(isinstance(ls, Son))
# print(isinstance(ls, Father))  # True  继承
# print(type(ls) is Son)  # 判断是否是一个内存地址
# print(type(ls) is Father)  # False  不考虑继承关系
# print(f'Son_id:{id(Son)}, father_id:{id(Father)}')

# is  是否引用同一个对象  即id是否相等
# ==  判断值是否相等

# 当对象有自己的实例属性的时候，就直接输出自己的属性
# 当对象没有该属性属性时候，才会去类对象中找

5.# 自省机制：查询对象的内部结构

class Person(object):
    name = 'haha'
class Student(Person):
    def __init__(self, school_name):
        self.school_name = school_name
hty = Student('logic_edc')
# print(hty.__dict__)  # {'school_name': 'logic_edc'} 当前对象的属性 {"属性":"属性值"}
# print(dir(hty))  # 考虑到继承的成员  返回类型是列表
# ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'name', 'school_name']

6. 重写父类的方法

class Person(object):
    def __init__(self,name,age,weight):
        self.name = name
        self.age = age
        self.weight = weight
    def speak(self):
        print(f"{self.name}说：我{self.age}岁")
class Student(Person):
    def __init__(self,name,age,weight,grade):
        # 调用父类的初始化方法
        # super().__init__(name,age,weight)
        Person.__init__(self,name, age, weight)
        self.grade = grade
    def speak(self):
        print(f"{self.name}说：我{self.age}岁,我在{self.grade}年级")
# hz = Student('小明',20,120,2)
# hz.speak()

7.多继承

class A(object):
    def __init__(self):
        print('A')
class C(A):
    def __init__(self):
        print('C')
        super().__init__()
class B(A):
    def __init__(self):
        print('B')
        super().__init__()
class D(B,C):
    def __init__(self):
        print('D')
        super().__init__()
if __name__ == '__main__':
    d = D()
    print(D.__mro__)