我在 UserList 下创建了一个名为 UList 的新类,它覆盖了该__add__
方法 - 它不允许将重复的项目添加到列表中。但是当我尝试运行它时,我没有得到预期的结果:
from collections import UserList
class UList(UserList):
def append(self,ap_item):
for ap in ap_item:
if ap in self:
raise ValueError(repr(ap) + " already exists in list")
else:
return UserList.append(self, ap_item)
def __add__(self,ad_item):
for ad in ad_item:
if ad in self:
raise ValueError(repr(ad) + " already exists in list")
else:
return UserList.__add__(self,ad_item)
def extend(self, ex_item):
for ex in ex_item:
if ex in self:
raise ValueError(repr(i) + " already exists in list")
else:
return UserList.extend(self,ex_item)
我怎样才能让这个方法正确执行?