内置方法

目录

• 内置方法

内置方法

1. __init__(完成对象的初始化)

   class Foo:
       def __init__(self,name,pwd):
           self.name = name
           self.pwd = pwd
   p = Foo('name','pwd')
   

2. _str__:如果不重写_str__ print打印会打印出内存地址

   class Foo:
       def __init__(self,name,pwd):
           self.name = name
           self.pwd = pwd
   p = Foo('name','pwd')
   print(p.__str__())#<__main__.Foo object at 0x00000239F5C69BC8>
   
   

   class Foo:
       def __init__(self,name,pwd):
           self.name = name
           self.pwd = pwd
       def __str__(self):
           return self.name
   p = Foo('name','pwd')
   print(p.__str__())#name
   # #相当于上面那句
   print(p)#name
   

   小知识

   l=[1,2,3]
   #本质也是调用list的__str__方法
   print(l)
   

3. _repr__：跟str类似,在交互式命令下直接写变量名,会执行_repr__

4. __getattr__:#如果去对象中取属性,一旦取不到,会进入到__getattr__

5. _selattr__:如果去对象中赋值属性,一旦取不到,会进入到_selattr__

6. __delattr__:#如果删除对象中的属性,会进__delattr__

   class Foo:
       def __init__(self,name):
           self.name = name
       def __getattr__(self, item):
           return 'getattr'
       def __set__(self, instance, value):
           return 'setattr'
       def __delattr__(self, item):
           return "delattr"
   f = Foo('nick')
   print(f.name)#nick
   
   print(f.age)#getattr,如果去对象中取属性,一旦取不到,会进入到__getattr__
   
   print(f.__dict__)#{'name': 'nick'}
   
   print(f.name)#nick
   
   f.sex = 'male'
   print(f.__dict__)#{'name': 'nick', 'sex': 'male'}
   
   
   del f.name #删除不掉，因为有delattr
   print(f.__dict__)#{'name': 'nick', 'sex': 'male'}
   

   原来字典使用方式

   di=dict(name='lqz',age=18)
   print(di)
   print(di['name'])
   print(di.name)
   di.sex='male'
   #
   

   写一个类继承字典,让它可以 . 取值,可以中括号取值

   class Mydict(dict):
       def __init__(self,**kwargs):
           #
           super().__init__(**kwargs)
   
       def __getattr__(self, item):
           #
           # print(item)
   
           return self[item]
       def __setattr__(self, key, value):
           self[key]=value
   
   
   
   di=Mydict(name='lqz',age=18)
   print(di['name'])
   print(di.name)
   di.sex='male'
   di['sex']='male'
   
   
   print(di['name'])
   print(di.name)
   di.sex=19
   print(di.sex)
   di['sex']='male'
   print(di.sex)
   
   
   

   __item__系列 对象通过[] 中括号取值,赋值,删除值的时候,会调用

   class Foo:
       def __init__(self, name):
           self.name = name
       def __getitem__(self, item):
           name=getattr(self,item)
           # print(name)
           # print(self.__dict__[item])
           return name
           # return self.__dict__[item]
       def __setitem__(self, key, value):
           print('obj[key]=lqz赋值时，执行我')
           self.__dict__[key] = value
       def __delitem__(self, key):
           print('del obj[key]时，执行我')
           self.__dict__.pop(key)
   
   f=Foo('nick')
   print(f['name'])
   
   __call__   对象加括号会调用它
   class Foo:
       def __call__(self):
           print('xxxx')
   
   f=Foo()
   f()
   

class Mydict():
    def __getattr__(self, item):
        print('xxx')
        return '该属性不存在'

m=Mydict()
print(m.name)