Functions in python give the optimized implementation of running logic of any program, multiple times with hassle-free execution. Decorators in python also revolve around the concept of Python functions. In this article, we will go through the Python Decorators in detail including various examples in this python decorator tutorial. The following topics are discussed in this blog.

Decorators in Python is an advanced topic. So before moving on make sure you are thoroughly clear with the concept of python functions. There are a few prerequisites that one must understand before moving on to decorators in Python.

First-Class Objects

Inner Functions

In python, everything is treated as an object including all the data types, functions too. Therefore, a function is also known as a first-class object and can be passed around as arguments.

Let’s take a look at an example to understand how it works.

In the above example, we have used the string interpolation to get the name and passed func1 and func2 as an argument in func3.

In python, it is possible to define functions inside a function. That function is called an inner function. Here is an example to show how we can use inner functions in python.

In the above program, it does not matter how the child functions are declared. The output depends on how the child functions are executed. They are locally scoped with the func() so they cannot be called separately.

If you call them separately you will get an error because they are stored as variables inside the func() and can be called only if func() is called.

Returning a function from a function

It is possible to return a function using another function. Take a look at the example below to understand this.

Decorators in python are very powerful which modify the behavior of a function without modifying it permanently. It basically wraps another function and since both functions are callable, it returns a callable.

In hindsight, a decorator wraps a function and modifies its behavior. Let us take a look at a simple example to understand how we can work with decorators in python.

To make things a little easier for the programmers, we have a syntactic sugar with python decorators. Take a look at an example below to understand how it works.

The output will be similar to the program above, the only difference is we have used the pie syntax with the @ symbol.

When you have a function with arguments, it becomes trickier for the decorator function since it also needs arguments in the declaration. To tackle this we can use the *args and **kwargs in the inner wrapper function. Take a look at the following example to understand this.

Let’s take a look at an example to see how we can return a value from a decorated function.

Make sure to return your wrapper function with arguments to avoid any errors.

Now that we know how decorators work in python, let us explore a rather complex features with the help of a few examples.

There are two ways to decorate a class in python. The first one is where you can decorate the methods inside a class, there are built-in decorators like @classmethod, @staticmethod and @property in python. @classmethod and @staticmethod define methods inside a class that is not connected to any other instance of a class. @property is normally used to customize the getters and setters of a class attribute. Lets take a look at an example to understand this.

Another way of decorating the class is by decorating the whole class. Let us take an example to understand this.

Decorating a class does not reflect on its methods. It is almost similar to writing a decorator of a function, the only difference is the class in the argument instead of a function.

A singleton class only has one instance. There are plenty of singletons in python including True, None, etc. Let us take a look at an example to understand this better.

Using ‘is’ only returns true for objects that are the same instance. The above example uses the same approach as any other function decorator. The only difference is we have used cls instead of function. Also, the first and second are the exact same instance.

You can use multiple decorators by stacking them on top of each other. Let us take an example to understand how this works.

This is how we can use nested decorators by stacking them onto one another. In the above example, it is only a mere depiction, for it to work you would have to define function1 and function2 with wrapper functions inside each of them.

It is always useful to pass arguments in a decorator. Let us consider the following example.

This brings us to the end of this article where we have learned how we can use Decorator in Python with examples. I hope you are clear with all that has been shared with you in this Python Decorator Tutorial

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