class List(list):

    def append(self, a_objcet):

        if type(a_objcet) is str:

            super().append(a_objcet)

        else:

            print('请传入字符转类型')

l1 = List('hello')

l1.append(123)

l1.append('world')

print(l1)

请传入字符转类型

['h', 'e', 'l', 'l', 'o', 'world']

Process finished with exit code 0

# 创建一个open方法

class Open:

    def __init__(self,filname,mode='r',encoding='utf-8'):

        self.fil = open(filname,mode,encoding=encoding)

        self.mode = mode

        self.encoding = encoding

    def __getattr__(self, item):

        print('-------->',item,type(item))

        return getattr(self.fil,item)

f1 = Open('a.txt','w')

print(f1.fil)

print(f1.read)             # 触发__getattr__

<_io.TextIOWrapper name='a.txt' mode='w' encoding='utf-8'>

--------> read <class 'str'>

<built-in method read of _io.TextIOWrapper object at 0x7f718a0007e0>

Process finished with exit code 0