[Python-ideas] An easier syntax for writing decorators(&similar things)?
Aaron Brady
castironpi at comcast.net
Thu Jan 24 03:06:19 CET 2008
> > >>>> 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:
> > >> [...]
> > >
> > >> 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 partial is as in functools and
> > prepartial(f, x, y)(z, t) <=> f(z, t, x, y)]
> >
> > Indeed, and if one restricts decorator_withargs to keyword arguments,
> > one can simply define it as:
> >
> > decorator_withargs = partial(partial, partial)
>
> I believe you can put -f- in the last pos'l argument and have this work.
>
> def mydec( arg0, arg1, f, before='entering %s', after='%s returns %%s').
>
> > Which is the curry operator! So decorator_withargs is some sort of
> > curry. In fact I had never realised before that this was a way to
> > define curry (for functions with 2 arguments)
> >
> > curry = partial(partial, partial)
> >
> > [if f is a two-arguments function then curry(f)(x)(y) is f(x, y)]
> >
> > This means that a meta-decorator (i.e. a decorator for decorators) is
> > a kind of currying operator.
> >
> > > Intriguing.
> >
> > !
def f( callback, *bar, **bkwar ):
def preg ( callfore, *far, **fkwar ):
sf= g( callback, callfore, bar, bkwar, far, fkwar )
return sf
return preg
We see how to rewrite this one?
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