[Python-Dev] The decorator module

[Phillip J. Eby]

At 07:55 AM 5/6/2005 -0700, Guido van Rossum wrote:
>[jJ]
> > > Incidentally, would the resulting functions be a bit faster if you 
> compiled
> > > the lambda instead of repeatedly eval ing it, or does the eval 
> overhead still
> > > apply?
>
>[Michele]
> > Honestly, I don't care, since "eval" happens only once at decoration time.
> > There is no "eval" overhead at calling time, so I do not expect to have
> > problems. I am waiting for volunteers to perform profiling and
> > performance analysis ;)
>
>Watch out. I didn't see the code referred to, but realize that eval is
>*very* expensive on some other implementations of Python (Jython and
>IronPython). Eval should only be used if there is actual user-provided
>input that you don't know yet when your module is compiled; not to get
>around some limitation in the language there are usually ways around
>that, and occasionally we add one, e.g. getattr()).

In this case, the informally-discussed proposal is to add a mutable 
__signature__ to functions, and have it be used by inspect.getargspec(), so 
that decorators can copy __signature__ from the decoratee to the decorated 
function.