Op vrijdag 25-12-2009 om 14:46 uur [tijdzone +0100], schreef Dirkjan
Ochtman:
> On Fri, Dec 25, 2009 at 12:33, Schneider <f.schnei...@de-bleek.demon.nl>
> wrote:
> > import clips
> >
> > class Callable(object):
> > def __init__(self, func):
> > self._func = func
> > clips.RegisterPythonFunction(func)
> > r = clips.BuildRule("%s-rule" % func.__name__,
> > "?f <- (duck)",
> > ""(retract ?f)
> > (python-call %s \"arg2py\")""" % func.__name__,
> > "The %s rule" % func.__name__)
> > print r.PPForm()
> > print "%s being initialized" % self._func.__name__
> >
> > def __call__(self, *args, **kwargs):
> > print "I am never executed"
> > return self._func(*args, **kwargs)
> >
> > class MyObject(object):
> >
> > @Callable
> > def MyMethod(self):
> > print "I am being called by CLIPS with the arg", self
> >
> > def Assert(self):
> > self.data = "DATA"
> > clips.Assert("(duck)")
> >
> > if __name__ == "__main__":
> > clips.Reset()
> > myObject = MyObject()
> > myObject.Assert()
> > clips.Run(100)
> > print "Bye"
> >
> > The output looks like:
> >
> > (defrule MAIN::MyMethod-rule "The MyMethod rule"
> > ?f <- (duck)
> > =>
> > (retract ?f)
> > (python-call MyMethod "arg2py"))
> >
> > MyMethod being initialized
> > I am being called by CLIPS with the arg arg2py
> > Bye
> >
> > Please note that the __call__ method in the decorator is not being called
> > from CLIPS.
>
> That's because you aren't calling any MyMethod here?
>
No, asserting the fact and giving the CLIPS engine the run instructrion
will fire the rule which does the python-call to MyMethod. As you see
from the output, this works since the output shows 'MyMethod being
initialized'
> > I don’t understand the internals but assume that calling a Python function
> > from a C program will not invoke __call__.
>
> I think "calling", which you can override in pure Python by defining a
> __call__ method, uses a call hook on the C-registered type. IOW, just
> attaching a method called __call__ to your C-defined class probably
> won't work, you need to attach it to the call hook on the C-level
> struct.
>
I am calling the python class method MyMethod from CLIPS, which is C.
When I call MyMethod from python, the __call__ in the decorator is
executed. Not in this case. I am not very familiair with decorators, so
there probably is a very good reason for this behaviour.
> Hope that helps (I haven't actually worked much with the C API myself),
>
> Dirkjan
More important than the __call__ issue, is the issue about encoding
something in Python that refers to the instance self, in a type that
CLIPS (C) can accept and return that in the python-call so I can use the
instance again.
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