Decorators Manage Functions and Classes, Too

Although much of the rest of this chapter focuses on wrapping later calls to functions and classes, I should underscore that the decorator mechanism is more general than this—it is a protocol for passing functions and classes through a callable immediately after they are created. As such, it can also be used to invoke arbitrary post-creation processing:

def decorate(O):
    # Save or augment function or class O
    return O

@decorator
def F(): ...                 # F = decorator(F)

@decorator
class C: ...                 # C = decorator(C)

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As long as we return the original decorated object this way instead of a wrapper, we can manage functions and classes themselves, not just later calls to them. We’ll see more realistic examples later in this chapter that use this idea to register callable objects to an API with decoration and assign attributes to functions when they are created.