Python has a "really hidden encapsulation"?

[Arnaud Delobelle]

dmytro starosud <d.starosud at gmail.com> writes:

>
> I think I'm being realized that Python allows to do everything.
> Maybe I will not try to find "really hidden encapsulation". :)

I think it's a wise decision :)

Just to challenge you a bit, here is another (doomed) attempt at having
private attributes for object instances:


def private_maker():
    class Private: pass
    privmap = {}
    def private(f):
        def wrapper(self, *args, **kwargs):
            priv = privmap.setdefault(self, Private())
            return f(self, priv, *args, **kwargs)
        return wrapper
    return private

private = private_maker()

class A:
    @private
    def __init__(self, private, x):
        private.x = x
    @property
    @private
    def x(self, private):
        return private.x

del private

a = A(2)


Can you change the value of a.x?

(Hint: my shortest solution is of the form A.*.*[*].*[*].x = 3)

> p.s. what do you think about the presence of two fields v_min (in
> first message):
> “s.__dict__['v_min']” and “s.v_min”?

Are you referring to the fact that in Python, if an attribute is a
property, the __dict__ lookup on the instance is not performed?  As in:

>>> class A:
...     @property
...     def x(self): return 42
... 
>>> a = A()
>>> a.__dict__['x'] = 24
>>> a.x
42
>>> a.__dict__['x']
24

This is documented, but I actually don't know the reason for it.

-- 
Arnaud