metaclasses

[castironpi at gmail.com]

On Mar 4, 12:51 am, Gerard Flanagan <grflana... at gmail.com> wrote:
> On Mar 4, 6:31 am, castiro... at gmail.com wrote:
>
>
>
>
>
> > On Mar 3, 10:01 pm, Benjamin <musiccomposit... at gmail.com> wrote:
>
> > > On Mar 3, 7:12 pm, castiro... at gmail.com wrote:
>
> > > > What are metaclasses?
>
> > > Depends on whether you want to be confused or not. If you do, look at
> > > this old but still head bursting essay:http://www.python.org/doc/essays/metaclasses/.
>
> > > Basically, the metaclass of a (new-style) class is responsible for
> > > creating the class. This means when Python sees
> > > class Foo(object):
> > >     __metaclass__ = FooMeta
> > > class FooMeta(type):
> > >     def __new__(cls, name, bases, dct):
> > >        #do something cool to the class
> > >        pass
> > > It asks FooMeta to create the class Foo. Metaclasses always extend
> > > type because type is the default metaclass.
>
> > But you can stack class decorations, but not class metas.
>
> > @somethingcool1
> > @somethingcool2
> > class Foo:
> >    pass
>
> > * class Foo:
> >    __metaclass__= MetaCool1, MetaCool
>
> > * denotes malformed
>
> -----------------------
> class Meta1(type):
>
>     def foo1(cls):
>         print 'hello'
>
> class Meta2(type):
>
>     def foo2(cls):
>         print 'castiron'
>
> class Meta(Meta1, Meta2):
>     pass
>
> class Base(object):
>     __metaclass__ = Meta
>
> Base.foo1()
> Base.foo2()

class Base(object):
   __metaclass__= type( 'Meta', ( Meta1, Meta2 ), {} )