第877页 | Learning Python | 阅读 ‧ 电子书库

Why Decorators?

Like many advanced Python tools, decorators are never strictly required from a purely technical perspective: their functionality can often be implemented instead using simple helper function calls or other techniques (and at a base level, we can always manually code the name rebinding that decorators perform automatically).

That said, decorators provide an explicit syntax for such tasks, which makes intent clearer, can minimize augmentation code redundancy, and may help ensure correct API usage:

 

Decorators have a very explicit syntax, which makes them easier to spot than helper function calls that may be arbitrarily far-removed from the subject functions or classes.Decorators are applied once, when the subject function or class is defined; it’s not necessary to add extra code (which may have to be changed in the future) at every call to the class or function.Because of both of the prior points, decorators make it less likely that a user of an API will forget to augment a function or class according to API requirements.

In other words, beyond their technical model, decorators offer some advantages in terms of code maintenance and aesthetics. Moreover, as structuring tools, decorators naturally foster encapsulation of code, which reduces redundancy and makes future changes easier.

Decorators do have some potential drawbacks, too—when they insert wrapper logic, they can alter the types of the decorated objects, and they may incur extra calls. On the other hand, the same considerations apply to any technique that adds wrapping logic to objects.

We’ll explore these tradeoffs in the context of real code later in this chapter. Although the choice to use decorators is still somewhat subjective, their advantages are compelling enough that they are quickly becoming best practice in the Python world. To help you decide for yourself, let’s turn to the details.