def addTwoNumbers(a, b):\n c=a+b\n return c\n\nc=addTwoNumber(4, 5)\n \nprint("Addition of two numbers=", c)<\/pre><\/div>\n\n\n\nOutput:<\/strong><\/p>\n\n\n\nAddition of two numbers=9<\/pre>\n\n\n\nNow our aim is to modify the behavior of addTwoNumbers()<\/code> without changing function definition and function call.<\/p>\n\n\n\nWhat function behavior do we want to change?<\/p>\n\n\n\n
We want addTwoNumbers<\/code> function should calculate the sum of the square of two numbers instead of the sum of two numbers.<\/p>\n\n\n\nHere is a simple decorator to change the behavior of the existing function.<\/p>\n\n\n\n
def decorateFun(func): \n def sumOfSquare(x, y): \n return func(x**2, y**2) \n return sumOfSquare \n\n@decorateFun\ndef addTwoNumbers(a, b): \n c = a+b \n return c \n\nc = addTwoNumbers(4,5) \nprint("Addition of two numbers=", c)<\/pre><\/div>\n\n\n\nOutput:<\/strong><\/p>\n\n\n\nAddition of two numbers=41<\/pre>\n\n\n\nThe below simple program is equivalent to the above decorator example. Here we are changing the function call.<\/p>\n\n\n\n
def decorateFun(func): \n def sumOfSquare(x, y): \n return func(x**2, y**2) \n return sumOfSquare \n\ndef addTwoNumbers(a, b): \n c = a+b \n return c \n\nobj=decorateFun(addTwoNumbers) \nc=obj(4,5) \nprint("Addition of square of two numbers=", c)<\/pre><\/div>\n\n\n\nOutput:<\/strong><\/p>\n\n\n\nAddition of square of two numbers=41<\/pre>\n\n\n\nNote:<\/strong> The number of arguments to the function inside the decorators should be the same as the number of arguments to the actual function.<\/p>\n\n\n\n