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comp.lang.python

Re: Simple Traits Questions

Robert Kern

3/28/2010 12:24:00 AM

On 2010-03-27 08:19 , Ethan Furman wrote:
> Okay, different post for my actual questions. :)
>
> On the PyPI page for strait (http://pypi.python.org/pypi/st...)
> it has the example of choosing which methods to keep in the composed class:
>
> class TOSWidget(BaseWidget):
> __metaclass__ = include(Pack, Place, Grid)
> info = Pack.info.im_func
> config = Pack.config.im_func
> configure = Pack.configure.im_func
> slaves = Pack.slaves.im_func
> forget = Pack.forget.im_func
> propagate = Pack.propagate.im_func
>
> My question is:
>
> Why use
>
> info = Pack.info.im_func
>
> instead of
>
> info = Pack.info
>
> ?

Pack.info is an unbound method object attached to the Pack class, not a function
object. It has some extra semantics on top of functions and is tied to the Pack
class. The .im_func attribute gets the actual function object underneath. When
defining the TOSWidget class, the objects defined in the suite under the class:
statement need to be actual functions in order to be turned into unbound methods
attached to the TOSWidget class.

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco