jython-users

[Jython-users] Making a class that acts as both a Python object and a Java object

[Kevin D. <kda...@we...>]

    Jython does a great job emulating Python objects in Java. It also,
through reflection, does a great job of letting you use Java methods, etc.
in Jython. It seems like it would be useful to have a base class that gives
you both sets of behavior out of the box:

- it would have a __dict__ to store things in
- it would use reflection to find out about Java methods
- it would look like a python class and allow you to use Jython's multiple
inheritance mechanism

This type of thing would allow you to easily build all sorts of extensions
to Jython. In situations where someone is more comfortable or it is more
convenient to do something in Java, you can still make objects that look
like python objects to Jython programs.

I'm just coming back to this after a couple of weeks away, but if memory
serves subclassing PyObject doesn't give __dict__ or reflection. Subclassing
PyInstance does give you a functional __dict__, but doesn't do reflection.
Subclassing PyClass actually can give both but PyClasses are not quite the
same. And there are a lot of private and protected members in there which
prevent easy subclassing.

Has anyone else been interested in such a thing? Any suggestions on an
approach to take?

Thanks,
Kevin

Re: [Jython-users] Making a class that acts as both a Python object and a Java object

[Kevin D. <kda...@we...>]

As a followup, here's a bit of code that illustrates:

public class MyClass extends SomePyThing
{
    public int sum(int val1, int val2)
    {
        return val1 + val2;
    }
}

--jython--
import MyClass
a = MyClass()
a.foo = 2
a.bar = 4
a.sum(a.foo, a.bar)

With a standard Java class, a.foo=2 would fail. With a subclass of
PyInstance, a.foo = 2 would work, but a.sum(...) would fail (AttributeError,
because it can't find the method since reflection isn't used).

Kevin

----- Original Message -----
From: "Kevin Dangoor" <kda...@we...>
To: <jyt...@li...>
Sent: Thursday, July 12, 2001 11:11 AM
Subject: [Jython-users] Making a class that acts as both a Python object and
a Java object


>     Jython does a great job emulating Python objects in Java. It also,
> through reflection, does a great job of letting you use Java methods, etc.
> in Jython. It seems like it would be useful to have a base class that
gives
> you both sets of behavior out of the box:
>
> - it would have a __dict__ to store things in
> - it would use reflection to find out about Java methods
> - it would look like a python class and allow you to use Jython's multiple
> inheritance mechanism
>
> This type of thing would allow you to easily build all sorts of extensions
> to Jython. In situations where someone is more comfortable or it is more
> convenient to do something in Java, you can still make objects that look
> like python objects to Jython programs.
>
> I'm just coming back to this after a couple of weeks away, but if memory
> serves subclassing PyObject doesn't give __dict__ or reflection.
Subclassing
> PyInstance does give you a functional __dict__, but doesn't do reflection.
> Subclassing PyClass actually can give both but PyClasses are not quite the
> same. And there are a lot of private and protected members in there which
> prevent easy subclassing.
>
> Has anyone else been interested in such a thing? Any suggestions on an
> approach to take?
>
> Thanks,
> Kevin
>
>
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