Python offers us many ways to create higher-order functions. In Chapter 5, Higher-order Functions, we looked at two techniques: defining a function which accepts a function as an argument and defining a subclass of Callable which is either initialized with a function or called with a function as an argument.

In this chapter, we'll look at using a decorator to build a function based on another function. We'll also look at two functions from the functools module, the update_wrapper() and wraps() functions, that can help us build decorators.

One of the benefits of decorated functions is that we can create composite functions. These are single functions that embody functionality from several sources. A composite function, , can be somewhat more expressive of a complex algorithm than . It's often helpful to have a number of syntax alternatives for expressing complex processing.