Example usage of decorators in Python

decorators.py

import os
import sys
from time import sleep


# Decorator @timer
def timer(func):
    def f(*args, **kwargs):
        before = time()
        rv = func(*args, **kwargs)
        after = time()
        print(f'Time spent in {func.__name__}: {after-before}s')
        return rv
    return f


@timer
def main():
    sleep(3)
    return None

    
if __name__ == '__main__':
    main()