Question

To what extent can a class “protect” one of it’s attributes from outside access?

For example, a class with a conventional _secret attribute, the original value is easily accessed:

class Paranoid(object):
    def __init__(self):
        self._secret = 0

    def set(self, val):
        self._secret = val * 10

    def get(self):
        return self._secret / 10

p = Paranoid()
p.set(123)
print p.get() # 123
print p._secret # 1230, should be inaccessible

How can access to _secret be made more difficult?

There’s no practical application to this, I’m just curious if there’s novel ways to make it more difficult to access (within the context of Python – so ignoring the fact you could, say, attach a debugger to the Python process and inspect the memory)

Answer 1

>>> def Paranoid():
...     _secret_dict = {'_secret': 0}
...     class ParanoidClass(object):
...             def set(self, val):
...                     _secret_dict['_secret'] = val * 10
...             def get(self):
...                     return _secret_dict['_secret'] / 10
...     return ParanoidClass()
... 
>>> p = Paranoid()
>>> p.set(123)
>>> p.get()
123

This reminds me of a Steve Yegge blog post.