面向对象高阶

isinstance,issubclass

isinstance:判断对象是否为这个类实例化出来的（会检测父类）

type:获取实例化出对象的类（不会检测父类）

class Foo:
    pass

class Bar(Foo):
    pass

b=Bar()
print(isinstance(b,Foo))  # True
print(isinstance(b,Bar))  # True

print(type(b)==Foo)  # Fasle
print(type(b)==Bar)  # True

issubclass:比较判断某个类是否为另一个类的子类

print(issubclass(Bar,Foo))  # True

反射

hasattr:通过字符串判断是否类属性存在

getattr:通过字符串获取类属性

setattr:通过字符串修改类属性

delattr:通过字符串删除类属性

class Foo:
    count=0
    def eat(self):
        print('eat')

f=Foo()
if hasattr(f,'eat'):  # 判断有没有
    getattr(f,'eat')()  # 获取

setattr(f,'ear',222)  # 修改自己，没有就添加
setattr(f,'count',111)

delattr(f,'count')  # 删除
print(f.__dict__)

项目中可能用到

import sys
import time

# comment.py 通用评论接口 
# import goods,shopping_car 导入其他文件
mod=sys.modules['__main__']
arg==input('goods.py或shopping_car.py给comment.py的参数)
if arg=='goods':
    tim=getattr(mod,'goods',None)
    # 2287273393
    # return comment 
elif arg=='shoppings_car':
    tim=getattr(md,'goods',None)
    # 150
    #return comment

call

class Foo:
    def __init__(self):
        print('Foo()会触发我')
    def __call__(self):
        print('Foo()()/f()会触发我')

f = Foo()  # 对象再加括号调用触发
f()

元类

元类用来造类的

元类()-->类-->init

元类()()-->对象-->call

类分为几部分：类名/类体名称空间/父类们

class Mymeta(type):
    def __init__(self,class_name,class_bases,class_dic):
        # 控制类的逻辑代码
        super().__init__(class_name,class_bases,class_dic)
    
    def __call__(self,*args,**kwargs):
        # 控制类实例化的参数
        
        obj = self.__new__(self)  # obj就是实例化的对象
        self.__init__(obj,*args,**kwargs)
        print(obj.__dict__)
        
        # 控制类实例化的逻辑
        
        return obj
    
class People(metaclass=Mymeta):
    def __init__(self,name,age):
        self.name = name
        self.age = age

单例模式

利用类的绑定方法的特性

NAME = 'nick'
AGE = 18

class People():
    
    __instance = None
    
    @classmethod
    def from_conf(cls):
        if cls.__instance:
            return cls.__instance
        
        cls.__instance = cls(NAME,AGE)
        return cls.__instance

People.from_conf()
People.from_conf()

利用装饰器

NAME = 'nick'
AGE = 18

def deco(cls):
    cls.__instance = cls(NAME,AGE)
    
    def wrapper(*args,**kwargs):
        if len(args) == 0 and len(kwargs) == 0:
            return cls.__instance
        
        res = cls(*args,**kwargs)
        return res
    
    return wrapper

@deco
class People():
    def __init__(self,name,age):
        self.name = name
        self.age = age

peo1=People()
peo2=People()

利用元类（正宗的）

NAME = 'nick'
AGE = 18

class Mymeta(type):
    def __init__(self,class_name,class_bases,class_dict):
        super().__init__(class_name,class_bases,class_dict)
        self.__instance = self(NAME,AGE)
     
    def __call__(self,*args,**kwargs):
        
        if len(args) == 0 and len(kwargs) == 0:
            return self.__instance
        
        obj = object.__new__(self)
        self.__init__(obj,*args,**kwargs)
        
        return obj
    
class People(metaclass=Mymeta):
    def __init__(self,name,age):
        self.name = name
        self.age = age
        
peo1 = People()
peo2 = People()

异常处理

捕捉异常

x = 10
y = 20
c = 30

try:
    1/0
except Exception as e:
    print(e)

raise

raise keyboardInterrupt('中断捕捉')

assert

判断某一行代码是否有问题