Revised PEP 318 - Function/Method Decorator Syntax

[Michele Simionato]

Andrew Bennetts <andrew-pythonlist at puzzling.org> wrote in message news:<mailman.1055253020.26604.python-list at python.org>...
> On Tue, Jun 10, 2003 at 12:25:13PM +0000, Kevin Smith wrote:
> [...]
> >     The proposed syntax is general enough that it could be used 
> >     on class definitions as well as shown below.
> > 
> >         class foo(object) as classmodifier:
> >             class definition here
> > 
> >     However, there are no obvious parallels for use with other
> >     descriptors such as property().
> 
> Note that you can already do tricky stuff with properties if you really want
> to define one all at once:
> 
>     class EvilProperty(type):
>         def __new__(cls, name, bases, d):
>             return property(d.get('get'), d.get('set'), d.get('del'), d['__doc__'])
>     
>     class C(object):
>         class x:
>             """An evil test property"""
>             __metaclass__ = EvilProperty
>             def get(self):
>                 print 'Getting'
>                 return 1
>             def set(self, value):
>                 print 'Setting to', value
>                 
>     c = C()
>     print c.x
>     c.x = 5  
>     print C.x.__doc__
> 
> This has the advantage that you can define your property in a single block,
> and you don't have to look too far ahead in the nested class to see the
> crucial "__metaclass__ = EvilProperty" line.
> 
> It does kinda feel like yet-another-gratuitous-use-of-metaclasses, though ;)
> 
> -Andrew.

Carl Banks posted something similar few days ago. Evil is a good name,
since x returns a property instance and not a class. I think he wrote
something like this:

class C(object):
    class x:
        """An evil test property"""
        def __metaclass__(name, bases, d):
            return property(d.get('get'), d.get('set'),
                            d.get('del'),d.get('__doc__'))
        def get(self):
            print 'Getting'
            return 1
        def set(self, value):
            print 'Setting to', value
      
I hope nobody will ever try this in production code!


                       Michele