Function Wrappers in Python

In Python, decorators, or wrappers over functions, are incredibly useful and powerful tools that let programmers change a function's or class's behavior. With the help of decorators, we may expand the behavior of a wrapped function without making permanent changes to it. Functions are called within the wrapper function after being sent as a parameter to another function in decorators.

Syntax:

This is also similar to

Let's examine the samples below to have a better idea.

Example 1:

Program Explanation:

The application shows how to use a Python decorator to provide extra functionality both before and after a function is executed. The main function is wrapped by the greet_decorator function, which prints messages both before and after the function is executed. The decorated_function applies the decorator to integrate this extra behaviour, and when it is called, it produces the predetermined messages in addition to the message from the original function.

Output:

 Greetings, this is before the main function runs. This message is inside the main function! message appears after main function runs. 

Example 2: Let's create a decorator that measures how long it takes the function to execute.

Program Explanation:

The decorator measure_execution is defined in this Python application to measure and display function execution times. The reverse_count method, which counts down from a given integer to zero, receives the decorator. The decorator reports the function's execution time when reverse_count is invoked.

Output:

 reverse_count executed in 0.000002 seconds reverse_count executed in 0.000060 seconds 

It is important to note that decorators typically do not change the function being wrapped's calling signature or return value. To ensure that any input arguments may be taken, *args and **kwargs are used. Almost often, a decorator's return value comes from calling func(*args, **kwargs), where func is the unwrapped function that was originally used.