Frank Millman wrote:
> I thought that the main point of using property was to prevent direct
> access to the attribute.
Not "prevent access to" as much as "add behaviour to".
Is this a valid comment, or does it come under the category of 'we are
all adults here'?
The latter. And the "__" doesn't provide much protection, really (as
we'll see below).
While experimenting, I came across the following curiosity.
I know that prefixing a class attribute with a double-underscore makes
it difficult to access the attribute externally. Here is a simple
example -
class Test(object):
... def __init__(self,x):
... self.x = x
... self.__y = 123
... def get_y(self):
... return self.__y
t = Test(99)
t.x
99
t.get_y()
123
t.__y
AttributeError: 'Test' object has no attribute '__y'
I was surprised that I could do the following -
t.__y = 456
t.__y
456
t.get_y()
123
It's not important, but I am curious to know what is going on
internally here.
hint:
>>> dir(t)
['_Test__y', ..., '__y', 'get_y', 'x']
>>> t._Test__y
123
>>> t.__y
456
</F>
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