[Python-3000] Type annotations: annotating generators

Guido van Rossum guido at python.org
Fri May 19 22:46:52 CEST 2006

On 5/19/06, Jim Jewett <jimjjewett at gmail.com> wrote:
> So the real question is how best to write "A callable with this
> signature".  I do not think the right answer is an inline recreation.
> Compare to
>     from inspect import signature as sig
>     def button_pushed(button,
>                       pressure=1,
>                       alarm=False,
>                       repeated=False, ...
>     # Give the signature a name, with ButtonFunc=sig(button_pushed) ?  nah...
>     def foo(self, action:sig(button_pushed)): ...

I like this idea. Maybe it could be called like() or Like(). (And it
still lets you inline if you really want: just put a lambda in there.
:-) Having this for the complex cases would make it possible to
simplify Function() to the bare minimum: fixed positional args and

> > Think about it: when's the last time you had a callback parameter that
> > was called with keyword arguments?
> It may be reasonable to require that the callback accept a keyword
> such as 'color', rather than requiring it to take all possible GUI
> parameters in a specific order.

May be. But somehow I don't see a big use case for a callback being
called with all possible keyword arguments. It's more likely that
you'd pass a single object containing all the UI parameterizations.

As I urged Collin before, can someone please come up with a realistic
motivating example? If there aren't any I will put my foot down and
call YAGNI on any mechanism to specify signatures with keyword
arguments, *args, or **kwds.

--Guido van Rossum (home page: http://www.python.org/~guido/)

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