How to add a Decorator to a Class Method

[davisn90210 at gmail.com]

On Nov 20, 12:32 pm, "gregpin... at gmail.com" <gregpin... at gmail.com>
wrote:
> On Nov 20, 2:05 am, Marc 'BlackJack' Rintsch <bj_... at gmx.net> wrote:
>
>
>
> > On Mon, 19 Nov 2007 20:59:51 -0800, gregpin... at gmail.com wrote:
> > > How do I add a decorator to a class method?  Here's what I want to do,
> > > but I guess my syntax isn't right.  Any advice?
>
> > > class A:
> > >     def pre(self,fn):
> > >         def new_func(*args,**kwargs):
> > >             print 'hi'
> > >             fn(*args,**kwargs)
> > >         return new_func
> > >     @self.pre
>
> > At this point there is no `self` which is exactly what the exception says
> > if you run this. This method definition executed at class definition time
> > so there is no instance of `A`.  You can't change it to `... at A.pre`` either
> > because the class is not fully constructed yet so the class name `A` does
> > not exist yet.  So you have to move `pre()` out of the class.
>
> > def pre(fn):
> >     def new_func(*args, **kwargs):
> >         print "'hi'"
> >         fn(*args, **kwargs)
> >     return new_func
>
> > class A(object):
> >     @pre
> >     def func(self, a, b):
> >         print a + b
>
> > a = A()
> > a.func(3, 5)
>
> > Ciao,
> >         Marc 'BlackJack' Rintsch
>
> Thanks those answers make sense.  But for this function if defined
> outside the class:
>
> > def pre(fn):
> >     def new_func(*args, **kwargs):
> >         print "'hi'"
> >         fn(*args, **kwargs)
> >     return new_func
>
> Can new_func reference self?  Would self just be one of the args?
>
> -Greg

For methods, self is always "just one of the args".  When the
decorator is applied to a method, self will be args[0] in new_func.

--Nathan Davis