Function Decorators in Python

First function decorator without arguments

def say_hi(func):
    def inner_wrapper():
        print("hi from decorator")
        func()

    return inner_wrapper


@say_hi
def actual_func():
    print("I am the actual function")


actual_func()

OUTPUT: 
>>> hi from decorator
    I am the actual function

Now, With fixed arguments

def validate_age(func):
    def validator(age: int):
        if age > 140 or age < 0:
            print("age is invalid")
        else:
            print("age is valid")

    return validator


@validate_age
def set_age(input_age: int):
    age = input_age


set_age(150)
set_age(50)

OUTPUT:
age is invalid
age is valid

Now, With variable number of arguments

You may first read this article which explained the use of *args and **kwargs. Because this concepts is used in decorators.

https://medium.com/lets-learn-python/use-of-args-and-kargs-3e3bf25853ff

This decorator function validates the paramaters of the report card of a school student.

• It validated if the name is in string format.
• It validated age to be >0 and <140
• It validated marks to be >0 and <100.