decorator chaining

def supper(f):

    def inner():

        #b=f()

        return f().upper()

    return inner

#@supper

def display():

    return "hello"

result=supper(display)

print(result())

print(display())

"""output:

HELLO

hello

"""

Whenever we would like to apply the decorator function to the existing function, it is mandatory to send existing function as a parameter to the decorator function.

Ex:

def décor (fun):

  …

def normal():

  …

result=décor(normal)

To apply the decorator function automatically to any normal function, use @ symbol followed by decorator name above the function definition.

@supper

def display():

    return "hello"

so no need to call the decorator function explicitly sending normal function as a paratmeter.

Decorator chaining: A python program to apply two decorators to the same function using @ symbol

#a decorator that increments the value of a function by 2

def decor1(fun):

    def inner():

        a=fun()

        return a*2

    return inner

#a decorator that doubles the value of a function

def decor2(fun):

    def inner():

        a=fun()

        return a+2

    return inner

#take a function to which decorator should be applied

@decor1

@decor2

def count():

    return 4

""

@decor1

@decor2 this is equalant to

#result=decor1(decor2(count))

#print(result())

"""

"""output:

12

"""

Note: décor, inner are user defined words, instead we can give any name convention.

Related Video: https://youtu.be/Vm4BnLWTK4E
https://youtu.be/dqVMIgkZRiQ
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