class MyTest:
    def __getattr__(self, item):
        #   当访问的属性不存在时，该方法会被触发
        print("触发__getattr__属性")
        super().__getattribute__(item)

mt = MyTest()
mt.name

执行结果：
    mt.name
  File "C:/Users/Administrator/PycharmProjects/untitled/test.py", line 32, in __getattr__
    super().__getattribute__(item)
AttributeError: ‘MyTest‘ object has no attribute ‘name‘
触发__getattr__属性

class MyTest:
    def __getattr__(self, item):
        #   当访问的属性不存在时（报AttrError异常时），该方法会被触发
        print("触发__getattr__方法")
        super().__getattribute__(item)

    def __getattribute__(self, item):
        #   当访问属性的时候，第一时间触发此方法去查找属性
        print("触发__getattribute__方法")
        return object.__getattribute__(self,item)



mt = MyTest()
mt.name

执行结果：
触发__getattribute__方法
Traceback (most recent call last):
触发__getattr__方法
  File "C:/Users/Administrator/PycharmProjects/untitled/test.py", line 43, in <module>
    mt.name
  File "C:/Users/Administrator/PycharmProjects/untitled/test.py", line 33, in __getattr__
    super().__getattribute__(item)
AttributeError: ‘MyTest‘ object has no attribute ‘name‘

class MyTest:

    def __setattr__(self, key, value):
        #   这个方法是在给对象设置属性的时候触发
        print("触发__setattr__方法")
        super().__setattr__(key,value)　　#　　key是属性名，value是属性值

mt = MyTest()
mt.name = 10
print(mt.name)

执行结果：
触发__setattr__方法
10

class MyTest:
    
    def __delattr__(self, item):
        # 这个方法在删除属性的时候触发
        print("触发__delattr__方法")
        super().__delattr__(item)  #   item是属性名

mt = MyTest()
mt.name = 10
del mt.name　　#　　删除属性
print(mt.name)

执行结果：
触发__delattr__方法
Traceback (most recent call last):
  File "C:/Users/Administrator/PycharmProjects/untitled/test.py", line 55, in <module>
    print(mt.name)
AttributeError: ‘MyTest‘ object has no attribute ‘name‘