[Python-Dev] Re: 2.4a2, and @decorators

[David Eppstein]

In article <110DAF75-E504-11D8-8D12-000A95A50FB2 at fuhm.net>,
 James Y Knight <foom at fuhm.net> wrote:

> >     @ foo or bar
> >     def f(): ...
> >
> > you can write
> >
> >     deco = foo or bar
> >     @deco
> >     def f(): ...
> 
> An even better workaround is to write:
>    def d(arg): return arg
> 
>    @d(foo or bar)
>    def f(): ...
> 
> However, it seems as if this restriction creates a new class of 
> expression for no gain. It is true enough that *most* python 
> expressions aren't useful to write after a @, but that's also true of a 
> lot of other places an expression can be used (e.g. before a () of a 
> function call. A list comprehension can never result in a callable 
> object. An arithmetic operation usually won't.).

As you say, there aren't a lot of types of Python expression that return 
callables.  The main thing this restriction seems to prevent is @lambda,
and I think preventing that is a good thing.  The other possibility that 
comes to mind is @functable[index], but I'd have to see a use case 
before worrying too much that it's not allowed.

-- 
David Eppstein
Computer Science Dept., Univ. of California, Irvine
http://www.ics.uci.edu/~eppstein/