Python基础27类-包装、组合方式授权、判断对象类型的方法

#包装标准类型
class List(list):
    def append(self,p_object):
        if type(p_object) is str:
            #self.append(p_objec) #无限递归
            super().append(p_object) #等价与list.append(p_object)
    def show_middle(self):
        mid_index=int(len(self)/2)
        return self[mid_index]
l=List('hello')
l.append('SB')
print(l)
print(l.show_middle())

#组合方式授权
class Filehandle:
    def __init__(self,filename,mode='r',encoding='utf-8'):
        self.filename=open(filename,mode,encoding=encoding)
        self.mode=mode
        self.encodig=encoding
    def __getattr__(self,item):
        return getattr(self.filename,item)

f1=Filehandle('aaa.txt')
print(f1.read())

#isinstance跟issubclass,type
class Foo:
    pass
f1=Foo()
print(isinstance(f1,Foo))
class Bar(Foo):
    pass
b1=Bar()
print(issubclass(Bar,Foo))
print(type(b1))