Dynamically creating propertys

[Nicodemus]

Timothy Grant wrote:

>Is it possible to dynamically create a property? I've got some code that uses 
>dynamically created attributes, but on looking at the new property stuff it 
>looks like that code could be significantly improved if I could use property 
>access instead.
>

You can add methods and attributes to a class after it was defined.
Suppose you have a class C, which has an attribute x, with getter and 
setter methods:

 >>> class C(object):
...     def __init__(self):
...             self._x = 0
...     def getx(self):
...             return self._x
...     def setx(self, x):
...             self._x = x
...
 >>> c = C()
 >>> c.getx()
0
 >>> c.setx(10)
 >>> c.getx()
10


Now you want the attribute '_x' to be accessed as a property, 'x'. The 
only thing you have to do is to create the property wrapper and add it 
to the class:

 >>> C.x = property(C.getx, C.setx)

And that's it.

 >>> c.x
10
 >>> c.x = 0
 >>> c.x
0


Note that you can also add methods to the class after it was defined. 
So, you can add the acessor methods if you only have the attribute:

 >>> class C(object):
...     def __init__(self):
...             self._x = 0
...
 >>>
 >>> def getx(self):
...     return self._x
...
 >>> def setx(self, x):
...     self._x = x
...
 >>> C.getx = getx
 >>> C.setx = setx
 >>> c = C()
 >>> c.getx()
0
 >>> C.x = property(C.getx, C.setx)
 >>> c.x
0
 >>> c.x = 10
 >>> c.x
10



Hope this helps,
Nicodemus.