Quick Check: Python Class Subscription and __class_getitem__

Review

1. Which special method can handle a subscription such as Box[int] when Box itself is the object being subscribed?

   __class_getitem__() is the class-subscription hook.
2. How must __class_getitem__() be decorated when it is defined directly on a class?

   Python supplies the class automatically for this special method.
3. Which method handles catalog[0] when catalog is an instance?

   Instance subscription is handled by __getitem__().
4. What can happen if a class’s metaclass defines __getitem__()?

   A metaclass __getitem__() can handle class subscription before __class_getitem__() is selected.
5. What is a common runtime representation returned by __class_getitem__() for a generic-style class?

   GenericAlias represents a parameterized generic class at runtime.