[Tutor] property built-in

[Python]

On Thu, 2006-10-19 at 19:03 +0200, thomas wrote:
> Hi,
> 
> 
> I was wondering some things about property.
> 
> suppose I have a class like this:
> 
> class A(object):
>     def __init__(self, x, y):
>        self.__x = x
> 
>     def x():
>        def get(self):
             fget
>           return self.__x
> 
>        def set(self, x):
             fset
>           self.__x = x
>           #and some other code that is important
         return locals()
> 
>     x= property(**x())
> 
> questions:
>     1: why doesn't there have to be a self in x()?

x is not a "normal" class method.  It is only used as a container to
hold the "real" methods which are returned in the locals() dictionary.

property supports keyword arguments fget, fset, fdel and doc.  The
definitions in your x method (Too many uses of x for different purposes)
MUST match the property keywords because of the use of locals().

>     2: how do I address the setter of x in the init?

Just use it.  Change __init__ to have  
	self.x = x

By the time __init__ is usable, 
	x = property( **x())
will have done its magic.  x will be a property of the class.


>>> class A(object):
...     def __init__(self, x, y):
...        self.x = x
...     def x():
...        def fget(self):
...           return self.__x
...        def fset(self, x):
...           self.__x = x
...           #and some other code that is important
...        return locals()
...     x= property(**x())
...
>>> a = A(1,2)
>>> a.x
1
>>> a.x=4
>>> a.x
4

> 
> I think these are basic questions, but I can't seem to find out how to 
> do it.
> 
> 
> Thanks
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
-- 
Lloyd Kvam
Venix Corp