Phillip J. Eby wrote: [SNIP]
One solution is to have a __signature__ attribute that's purely documentary. That is, modifying it wouldn't change the function's actual behavior, so it could be copied with update_meta() but then modified by the decorator if need be. __signature__ would basically be a structure like the one returned by inspect.getargspec(). Also, 'instancemethod' would have a __signature__ equal to its im_func.__signature__ with the first argument dropped off, thus making it easy to introspect wrapper chains.
I discussed this approach with Guido in private e-mail a few months back during discussion about an article I was writing for DDJ about decorators. We also discussed something very similar to 'update_meta()', but never settled on a name. Originally he wanted me to PEP the whole thing, but he wanted it to include optional type declaration info, so you can probably see why I haven't done anything on that yet. :)
However, if we can define a __signature__ format that allows for type declaration, I imagine there'd be little problem with moving forward on it.
It could be as simple as just a bunch of tuples. The following (assuming *args and **kwargs are not typed; don't remember if they can be)::
def foo(pos1, pos2:int, key1="hi", key2=42:int, *args, **kwargs): pass
could be::
((('pos1', None), ('pos2', int)), (('key1', "hi", None), ('key2', 42, int)),
'args', 'kwargs')In case the format is not obvious, just a bunch of tuples grouped based on whether they are positional, keyword, or one of the collecting arguments. For positional arguments, have a two-item tuple consisting of the argument name and the possible type. For keyword, 3-item tuple with name, default value, and possible type. Lacking *args and/or **kwargs could just be set to None for those tuple positions.
Since this is mainly for introspection tools the format can stand to be verbose and not the easiest thing to read by eye, but it must contain all possible info on the arguments. And if actual execution does not use this slot, as Phillip is suggesting, but it is only for informative purposes we could make it optional. It could also be set it to a descriptor that dynamically creates the tuple when called based on the function passed into the descriptor at creation time. This could be rolled into the update_meta (or whatever it ends up being called) function.
-Brett _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
