• 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

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  • 原文地址:https://www.cnblogs.com/gaohuayan/p/11066559.html
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