Is there anyway to selectively inherit/import a class/module?

[Peter]

On Jan 4, 12:06 pm, Steven D'Aprano <steve
+comp.lang.pyt... at pearwood.info> wrote:
> On Tue, 03 Jan 2012 14:21:36 -0800, Peter wrote:
> > I have a program that talks to a device via a serial interface.
> > Structurally it looks like this:
>
> > Program A -> module B -> Serial
>
> I don't understand what this means. Program A points to module B, which
> points to ... what is Serial? Where is it? Is it a class inside the
> module, or another module?
>
> > I want to add a protocol layer around the serial port without modifying
> > any of the modules above and I want to be able to use BOTH cases of the
> > program whenever convenient,
>
> Where are you using them from? Program A, or another program?
>
> I don't see any way to add the extra functionality to Program A without
> modifying Program A. But if you're okay with that, here's a way to
> conditionally define a class to use:
>
> # inside Program A
> import moduleB
>
> if condition:
>     Serial = moduleB.Serial  # I assume moduleB has a Serial class
> else:
>     class Serial(moduleB.Serial):  # subclass
>         def mymethod(self):
>             pass
>
> connection = Serial(...)
>
> > so at first it seemed like a simple case of
> > sub-classing the Serial class and then (this is the problem) somehow use
> > either the original serial class definition when I wanted the original
> > program functionality or the new class when I wanted the extra layer
> > present.
>
> No problem. Here's another way to do it:
>
> from moduleB import Serial as SimpleSerial
> class ComplexSerial(SimpleSerial):
>     ...
>
> And now you can use both at the same time.
>
> --
> Steven

Thanks :-)