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Signature-preserving decorators

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  Signature-preserving decorators Henrik Faber <hfaber@invalid.net> - 2011-12-13 14:36 +0100
    Re: Signature-preserving decorators Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-13 09:26 -0700

#17135 — Signature-preserving decorators

Hi group,

when decorating a method in Python3, by use of the
functools.update_wrapper function, it can be achieved that the docstring
and name of the original function is preseverved.

However, the prototype is lost: When looking into the Python help, I
have lots of entries that look like:

getfoo(*args, **kwargs) -> int

setbar(*args, **kwargs)

As you can imagine, this is really not very self-explanatory. I've seen
a solution which constructs a wrapper's wrapper function using
inspection and eval -- this looks really dirty to me, however. Then
there's the "decorator" external module -- but I'd like to do it with
on-board tools.

Is this possible in Python3 with too much of a hassle?

Best regards,
Joe

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#17148

On Tue, Dec 13, 2011 at 6:36 AM, Henrik Faber <hfaber@invalid.net> wrote:
> Hi group,
>
> when decorating a method in Python3, by use of the
> functools.update_wrapper function, it can be achieved that the docstring
> and name of the original function is preseverved.
>
> However, the prototype is lost: When looking into the Python help, I
> have lots of entries that look like:
>
> getfoo(*args, **kwargs) -> int
>
> setbar(*args, **kwargs)
>
> As you can imagine, this is really not very self-explanatory. I've seen
> a solution which constructs a wrapper's wrapper function using
> inspection and eval -- this looks really dirty to me, however. Then
> there's the "decorator" external module -- but I'd like to do it with
> on-board tools.
>
> Is this possible in Python3 with too much of a hassle?

The decorator module also uses inspection and eval to do it, by the
way.  Currently there is no pretty way to do it that I know of, but
see PEP 362:

http://www.python.org/dev/peps/pep-0362/

That PEP has unfortunately been in the "Open" state for quite a long
time now, but it seems to me that a lot of people are starting to get
interested in this issue, so maybe it will start to pick up some steam
before too long.

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