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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 woul

• btown 7y ago
  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/functional/ 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!