[bgschiller]

I think I'm confused. If you want to delegate _everything_, why not just actually use inheritance? Or even the object itself. What's an example of when you would want an ObjectProxy?

Definitely agree about metaclass magic being a blessing and a curse. That superdelegate library was fun to write and uses a metaclass to make the API pleasant.

[btown]

If you don't know what you're going to need to wrap (heck, it might be something with methods implemented with native code), but you want to override or intercept a certain subset of calls, then composition/delegation is really the only thing you can do. It's significantly more stable than trying to find the class of an arbitrary object at runtime, create a subclass of it, and try to copy the state of the original object.

For instance, I've seen instrumentation libraries monkey-patch database cursors with wrappers around those cursors, so the library can detect usage of the cursor without changing its behavior.

Django itself has a LazyObject class, which operates similarly to an ObjectProxy but only evaluates its wrapped initializer when one of its properties is accessed: https://docs.djangoproject.com/en/2.2/_modules/django/utils/...

And I'm using wrapt in a project (which I hope to open source) where, by recursively wrapping the return value of every __getitem__ and __getattr__ with a properly-bookkept proxy object, you can see what subgraph of a complicated object hierarchy was actually used by a function call (say, the rendering of a Django or Jinja template). Possibilities of such a transformation are endless!