Signature-preserving decorators

[Henrik Faber]

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

 

[Ian Kelly]

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.