在 Python 中修改 class 个实例

Modifying class instances in Python

我有一个小class:

import pickle
import shelve

class Base:

    def __init__(self, userid, username, pic_list=[]):
        self.userid=userid
        self.pic_list=pic_list
        self.username_list=[username]
        self.username=self.username_list[-1]

    def pic_add(self, pic):
        self.pic_list.append(pic)

if __name__ == '__main__':

    path="D:/"

    db = shelve.open(path+'test_base')

    db['111']=Base('111','111name',[4,5,6])
    db['111'].pic_add('123dsf')

    print (sorted(db['111'].pic_list))

    db.close()

我想将 123dsf 附加到 class 实例“111”的 pic_list。但是我得到的结果是:

[4, 5, 6]
[Finished in 0.3s]

我想收到 [4, 5, 6, 123dsf]。我做错了什么?

谢谢。

P.S。提示 - 这是搁置模块语法的东西,'cos 添加 'y' 工作正常:

db['111']=Base('111','111name',[4,5,6])
db['111'].pic_add('123dsf')
Base.pic_add(db['111'],'123dsf')

y=Base('222','222name',[7,8,9])
y.pic_add('pis')

print (y.pic_list)

print (sorted(db['111'].pic_list))

结果是:

[7, 8, 9, 'pis']
[4, 5, 6]
[Finished in 0.4s]

两种方法 - 如文档中所建议:https://docs.python.org/2/library/shelve.html#shelve-example

1. 设置 writeback 标志:

db = shelve.open(path+'test_base', writeback=True)

允许您就地改变对象:

db['111'].pic_add('123dsf')

2. 检索存储对象的副本,然后变异副本,然后存储副本:

cpy = db['111']
cpy.pic_add('123dsf')
db['111'] = cpy