python 魔法函数

import numbers
class Group():
    def __init__(self,group_name,company_name,staffs):
        self.group_name=group_name
        self.company_name=company_name
        self.staffs=staffs
    def __getitem__(self, item):# for in __contains__ __iter__
        print(type(self))
        if isinstance(item,slice):
            return Group(self.group_name,self.company_name,self.staffs[item])
        elif isinstance(item,numbers.Integral):
            return self.staffs[item]
    def __reversed__(self):#reversed
        return self.staffs[::-1]
    def __iter__(self):#for in
        return iter(self.staffs)
    def __contains__(self, item):#in
        return item in self.staffs
    def __len__(self):#len
        return len(self.staffs)
    def __setitem__(self, key, value):
        self.staffs[key]=value
group=Group('test','staff',['aa','bb','cc','dd','ee'])
# group[2]=11
# print(group[::2])
print("ac" in group)
print(len(group))
print(reversed(group))