Why you may need them and how to implement a custom one
Decorators can seem a little mysterious when dealing with them for the first time, but without any doubt, it’s a great tool to enhance a function’s behavior.
In fact, there are two types of decorators in Python — class decorators and function decorators — but I will focus on function decorators here.
Before we get into the fun details of how a basic decorator works and how to implement your own decorators, let’s see why we need them in the first place. There are a few situations where decorators are of huge help.
They can add logging or instrumentation code and extract various metrics such as timing from application components in an encapsulated manner.
Decorators can be the perfect mechanism to validate input, which is especially important when working in dynamically typed languages like Python.
Built-in decorators are quite widely used in Python libraries. Typical examples include decorators for routing and authorization in web frameworks, for instance, the @route()decorator in Flask.
Now that we see that it’s a good idea to learn to write and apply decorators, let’s figure out what a decorator is and how to implement a custom decorator if needed.
The fundamentals that you need to know in order to work with decorators are that functions are also objects in Python, and they can be passed as arguments to other functions like any other object e.g. strings. Therefore, functions in Python are first-class objects.
Functions that take other functions as arguments and return a function are higher-order functions. Which is the case of Python decorators.
A function can be defined within another function. In that case it’s called a nested function. The other concept that is directly tied to nested functions and that you need to understand is closure — a function object that “remembers” data e.g. variables and their values from its enclosing scope. This will be the wrapper() function in our decorator example that we’ll see later.
A decorator is generally defined as a function that modifies the behavior of another function. Most often, a…
