Understand Python Decorators in 3 Minutes

Extend the functionality of methods and classes with decorators

Photo by the author.

Decorators provide a readable way of extending the functionality of a function, method, or class from outside of it. Using decorators is especially useful when decorating (i.e. extending) similar functions to do the exact same thing without adding unnecessary repetition in your code.

Here is an example of how to extend a function with a decorator:

@guard_zero
def divide(x, y):
    return x / y

The @guard_zero decorator extends the functionality of the divide method to ensure that no divisions are made by 0. However, at this point, there is no such thing as guard_zero because you haven’t implemented it yet. In the next section, I’m going to show you exactly how to do it.

How To Create a Decorator in Python

The best way to demonstrate decorators in action is by creating one and using it. Let’s implement the @guard_zero decorator.

In the beginning, you only have this method that divides two numbers:

def divide(x, y):
    return x / y

The issue with this method is that there is no check for whether the value y is 0. You could obviously solve the issue with a little if check. But there is an alternative: decorators.

Let’s start by creating a guard_zero decorator:

A decorator is like a regular function in Python. All it does is accept the operate function as an argument. Then it extends the functionality of operate by creating an inner function and adding the extended behavior there. Finally, it returns the inner function, which is now a new version of the operate function.

At this point, the guard_zero decorator is ready. You can now extend (i.e. decorate) the divide function like this:

divide = guard_zero(divide)