OOP techniques in Python

[Philippe Martin]

Why is that ? to me it makes sense when I see self.__m_var that I'm dealing
with a member variable taht derived classes will not see/access.

Philippe




Steven Bethard wrote:

> Panos Laganakos wrote:
>> we usually define private properties and provide public functions
>> to access them, in the form of:
>> get { ... } set { ... }
>> 
>> Should we do the same in Python:
>> 
>> self.__privateAttr = 'some val'
>> 
>> def getPrivateAttr(self):
>>     return self.__privateAttr
>> 
>> Or there's no point in doing so?
> 
> There is no point in doing so.  You should use plain attributes whenever
> possible (that is, whenever you're really just doing a get or a set,
> with no computation).  The only reason to use getters and setters is so
> that you can change the implementation later if you need to.  But python
> allows you to do this with properties:
> 
>  >>> class C(object):
> ...     def __init__(self, x):
> ...         self.x = x
> ...
>  >>> C(42).x
> 42
>  >>> class C(object):
> ...     def _get_x(self):
> ...         return self._x * 2
> ...     def _set_x(self, value):
> ...         self._x = value / 2
> ...     x = property(_get_x, _set_x)
> ...     def __init__(self, x):
> ...         self.x = x
> ...
>  >>> C(42).x
> 42
> 
> Which should not be interpreted as saying you should start writing a
> bunch of properties now. ;) Instead, only introduce a property when you
> find that something must remain an attribute (presumably for backwards
> compatibility reasons) but for whatever reason it now needs some
> additional computation.
> 
> STeVe