[Python-ideas] An easier syntax for writing decorators (&similar things)?

[Aaron Brady]

This is like totally. cool.  Like Mr. Delobelle's post on the decorator's
and stuff was like, a simplified version of this: 

decorator_withargs= partial( partial, prepartial )

Which is way cool, and I couldn't even understand, and like, wrap my brain
around and stuff.  Do uuuu understand?  It?

> -----Original Message-----
> From: python-ideas-bounces at python.org [mailto:python-ideas-
> bounces at python.org] On Behalf Of Guido van Rossum
> Sent: Wednesday, January 23, 2008 9:19 AM
> To: python-ideas at python.org
> Subject: Re: [Python-ideas] An easier syntax for writing decorators
> (&similar things)?
> 
> I'm wondering, will Aaron ever realize that no-one understands his posts?
> 
> On Jan 23, 2008 1:44 AM, Aaron Brady <castironpi at comcast.net> wrote:
> > > -----Original Message-----
> > > On 8 Oct 2007, at 10:57, Arnaud Delobelle wrote:
> > > >
> > > > On Mon, October 8, 2007 4:33 am, Adam Atlas wrote:
> > > >> When writing decorators especially when it's one that needs
> arguments
> > > >> other than the function to be wrapped, it often gets rather ugly...
> > > [...]
> > > > Whhy not create a (meta-)decorator to do this? Something like:
> > > [...]
> >
> > Following up post from 10/8/07.
> >
> > > To follow up on my untested suggestion, here's one that is tested:
> > >
> > > # This metadecorator hasn't changed
> > >
> > > def decorator_withargs(decf):
> > >      def decorator(*args, **kwargs):
> > >          def decorated(f):
> > >              return decf(f, *args, **kwargs)
> > >          return decorated
> > >      return decorator
> >
> > This is equivalent to:
> > (1)
> >       decorator_withargs= partial( partial, prepartial )
> >
> > , where prepartial is roughly the same as partial as you might expect:
> >
> > (2)
> > 1     def prepartial(func, *args, **keywords):
> > 2           def newfunc(*fargs, **fkeywords):
> > 3               newkeywords = keywords.copy()
> > 4               newkeywords.update(fkeywords)
> > 5               return func(*(fargs+ args), **newkeywords)
> > 6           newfunc.func = func
> > 7           newfunc.args = args
> > 8           newfunc.keywords = keywords
> > 9           return newfunc
> >
> > Partial is the same outside of line 5:
> >
> > (3)
> > 5               return func(*(args + fargs), **newkeywords)
> >
> > Results are the same:
> >
> > -> f
> > 1
> > f -> 2
> > 2
> >
> > Intriguing.
> >
> > > # Here's how to use it to create a decorator
> > >
> > > @decorator_withargs
> > > def mydec(f, before='entering %s', after='%s returns %%s'):
> > >      before = before % f.__name__
> > >      after = after % f.__name__
> > >      def decorated(*args, **kwargs):
> > >          print before
> > >          result = f(*args, **kwargs)
> > >          print after % result
> > >          return result
> > >      return decorated
> > >
> > >
> > > # Now I can decorate a function with my new decorator
> > >
> > > @mydec(before='-> %s', after='%s -> %%s')
> > > def f(x):
> > >      print x
> > >      return x+1
> > >
> > >
> > > Then
> > >
> > >  >>> f(1)
> > > -> f
> > > 1
> > > f -> 2
> > > 2
> > >
> > > --
> > > Arnaud
> >
> > _______________________________________________
> > Python-ideas mailing list
> > Python-ideas at python.org
> > http://mail.python.org/mailman/listinfo/python-ideas
> >
> 
> 
> 
> --
> --Guido van Rossum (home page: http://www.python.org/~guido/)
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