This chapter introduces a collection of more advanced function-related topics: recursive functions, function attributes and annotations, the lambda expression, and functional programming tools such as map and filter. These are all somewhat advanced tools that, depending on your job description, you may not encounter on a regular basis. Because of their roles in some domains, though, a basic understanding can be useful; lambdas, for instance, are regular customers in GUIs.

Part of the art of using functions lies in the interfaces between them, so we will also explore some general function design principles here. The next chapter continues this advanced theme with an exploration of generator functions and expressions and a revival of list comprehensions in the context of the functional tools we will study here.