What are Function Decorators and how to define them in Python Program

How to define Function Decorators in Python Program

In Python, we can extend and modify the behavior of a callable functions, methods or classes without permanently modifying(eg: the original definition of the function as it is) the callable by using decorators.

The Function decorators are functions which accepts function references as arguments and adds a decorator or wrapper or additional functionality around them and returns the function with the additional(wrapper) features as a new function.

To apply the decorator(wrapper function) to any function, we can use the '@' symbol along with the decorator function name just before the actual function for which you wants to apply.

Example:

Now lets define a decorator(wrapper) function which helps to find the total time taken for the execution of a function.

import time

def exe_time(func):  # Outer function

    def wrapper(*args, **kwargs):  # Inner function

        st_time = time.time()

        result = func(*args, **kwargs)

        en_time = time.time()

        print('The execution time of '+ func.__name__ + ' is: ' + str(round((en_time-st_time)*1000, 2))+' milli sec.')

        return result

    return wrapper

Now we can use this exe_time() function as a decorator to the following functions.

@exe_time  # Decorator or wrapper function

def func_square(n):  # The original Function

    x = []

    for k in n:

        x.append(k*k)

    return x

@exe_time  # Decorator or wrapper function

def func_cube(n):  # The original Function

    y = []

    for k in n:

        y.append(k*k*k)

    return y

Now lets pass a list of values to the above functions :

lst = range(1, 100000)

op_square = func_square(lst)

# print('The squares of list of numbers is: ', op_square)

op_cube = func_cube(lst)

# print('The cubes of list of numbers is: ', op_cube)

# Result:

The execution time of func_square is: 22.13 milli sec.

The execution time of func_cube is: 46.87 milli sec.

#--------------------------------------------------------------Thanks--------------------------------------------------------------#