Xuanyi Wang_Day-5&6_Homework_04/05/23

The assignment for tonight is to write a class named Vault containing an attribute named "treasure" which returns "gold" under normal circumstances, but a warning message such as "attribute deleted!" if it detects any of its attributes have been changed. You can use the descriptor protocol (set, etc) to detect if its attributes have been changed, and it will have to check its own dict against a known good copy before accessing the treasure attribute to make sure that the attributes are what they're supposed to be.

class Vault:
    def __init__(self):
        self._treasure = 'gold'
        self._dict_copy = self.__dict__.copy()

    def __setattr__(self, name, value):
        if name != '_dict_copy' and name != '_treasure':
            if self.__dict__ != self._dict_copy:
                print("attribute deleted!")
            self._dict_copy = self.__dict__.copy()
        super().__setattr__(name, value)

    @property
    def treasure(self):
        if self.__dict__ != self._dict_copy:
            print("attribute deleted!")
            self._dict_copy = self.__dict__.copy()
        return self._treasure

An example usage of the `Vault` class:

vault = Vault()
print(vault.treasure)

Output:

attribute deleted!
gold

Change an attribute of the vault instance

vault.key = 'silver'

Output:

attribute deleted!

Try to access the treasure attribute again

print(vault.treasure)

Output:

attribute deleted!
gold

Another way to implement Vault:

class Vault:
    def __init__(self):
        self._known_attrs = {'treasure': 'gold'}
        self._attrs = self._known_attrs.copy()

    def __getattribute__(self, name):
        if name == 'treasure':
            attrs = object.__getattribute__(self, '_attrs')
            known_attrs = object.__getattribute__(self, '_known_attrs')
            if attrs != known_attrs:
                print('attribute deleted!')
            return attrs[name]
        return object.__getattribute__(self, name)

    def __setattr__(self, name, value):
        if name == 'treasure':
            attrs = object.__getattribute__(self, '_attrs')
            attrs[name] = value
            known_attrs = object.__getattribute__(self, '_known_attrs')
            if attrs != known_attrs:
                print('attribute deleted!')
        else:
            object.__setattr__(self, name, value)
vault = Vault()
print(vault.treasure)

Output:

gold

Change an attribute of the vault instance

vault.treasure = 'silver'

Output:

attribute deleted!

To get the other person's class to return "gold", despite any countermeasures they've implemented:

It can be achieved by creating a new class that inherits from the `Vault` class and overrides its `_treasure` attribute.

class OthersVault(Vault):
    def __init__(self):
        super().__init__()
        self._treasure = 'gold'

Create a `OthersVault` object that inherits all methods and attributes from the `Vault` class and returns 'gold' as the value of the `_treasure` attribute:

>>> gv = OthersVault()
>>> gv.treasure
'gold'

Xuanyi Wang_Day-5&6_Homework_04/05/23

An example usage of the Vault class:

Output:

Change an attribute of the vault instance

Output:

Try to access the treasure attribute again

Output:

Another way to implement Vault:

Output:

Change an attribute of the vault instance

Output:

It can be achieved by creating a new class that inherits from the Vault class and overrides its _treasure attribute.

Create a OthersVault object that inherits all methods and attributes from the Vault class and returns 'gold' as the value of the _treasure attribute:

An example usage of the `Vault` class:

It can be achieved by creating a new class that inherits from the `Vault` class and overrides its `_treasure` attribute.

Create a `OthersVault` object that inherits all methods and attributes from the `Vault` class and returns 'gold' as the value of the `_treasure` attribute: