Класс: вложенность экземпляров в экземпляр

class Block:
 
    def __init__(self, title, value):
        self.title = title
        self.value = value
 
    def get_block(self):
        return self.title, self.value

class Box:
    
    def __init__(self, name):
        self.name = name
        self.list_block = []
 
    def add_block(self, block):
    ''' метод добавляет экземпляр класса блок'''
        self.list_block.append(block)

class Client:
    
    def __init__(self,name):
        self.name = name
        self.data = []
 
    def add_data(self, box):
        self.data.append(box)

name = ['name', 'name_1', 'name_2']
list_client = [Client(n,p) for n,p in zip(name,passw)]
box_name = ['one', 'two', 'three']
 
 
for client in list_client:
    for name in box_name:
        box = Box(name)
        
        for block_data in (['data', 'val'],['data_1', 'val_1'],['data_2','val_2']):
            block = Block(*block_data)
            box.add_block(block)
        client.add_data(box)
 
 
print('\n#########################################\n')
 
def info(client):
    print(' ',client.name, client.passw)
    for box in client.data:
        print('   ',box.name)
        for block in box.list_block:
            print('     ',block.get_block())  
    print('\n#########################################\n')
 
for client in list_client:
    info(client)
 
# замена блока пользователя в боксе с заданным именем
for i, person in enumerate(list_client):
    if person.name == 'name_1':
        person = list_client[i] 
        for j, box in enumerate(person.data):
            if box.name == 'three':
                box = person.data[j]
                for x, block in enumerate(box.list_block):
                    if block.title == 'data_2':
                        box.list_block[x] = Block('nev_title', 'nev_val')
                        
 
for client in list_client:
    info(client)

>>> import shelve
>>> with shelve.open('st.dat') as f:
    f['Vic'] = {'url':'mail.ru','login':'noname','pass':'blabla'}
    f['Nick'] = {'url':'mail.ru','login':'noboby','pass':'blablabla'}
    
>>> f.close()
>>> f = shelve.open('st.dat')
>>> list(f.keys())
['Vic', 'Nick']
>>> f['Vic']
{'url': 'mail.ru', 'login': 'noname', 'pass': 'blabla'}
>>> f['Nick']
{'url': 'mail.ru', 'login': 'noboby', 'pass': 'blablabla'}
>>>

import shelve
import json
import base64
 
'''
формат данных - [[url,login,password],[url,login,password],...]
'''
 
def crypto(obj):
    return base64.b85encode(json.dumps(obj).encode())
 
def encrypto(value):
    return json.loads(base64.b85decode(value))
    
with shelve.open('pass.dat') as db:
    
    db['Vic'] = crypto([
                ['mail.ru','vic','blabla'],
                ['list.ru','vic1','bla bla'],
                ['ya.ru','VicT','bla'],
                ])
    db['Joe'] = crypto([
                ['mail.ru','joe','блаблабла'],
                ['list.ru','joE','парол'],
                ])
    
db.close()
 
 
with shelve.open('pass.dat') as f:
    for key,value in f.items():
        print(key,value)
        print(key,encrypto(value))