Decorator in Python, What is Decorator, how to define decorator, how to call decorator, what is @ symbol in python

It is used to access the features to function in python without changes in the actual function code. the decorator will be defined using @symbol.

The decorator provides extra features to the Python function.
In Python script, every variable, function, and other identifier managed by Object. hence function contains a unique address using function name.

It is used to modify the functionality of the function without modification of the actual function code.

Now I am creating two different programs to explain decorators in Python:-

Example 1:-

def displaypricegst(func):

    def func(p):

        print("Price with GST",p+p*0.20)

    return func    

  @displaypricegst

def displayPrice(price):

    print("Actual price",price)

displayPrice(100)    

Example2:-

def funnew(func):        #this will contain new features and old features both

    print("world")

    return func

  def createnew(func):     #this will contain only new features

    def innerfun():

        a=100

        b=200

        c=a*b

        print(c)

    return innerfun    

@funnew                #  funnew(fun)

def fun():

    print("hello")

fun()

 @createnew             #  createnew(addition)

def addition():

    a=100

    b=200

    c=a+b

    print(c)

addition()

Some Specific Features of Python User-Define Function:-

We can assign the address of a function to another function or another reference variable to call the function with a different name.
In this example, I am creating a program for an addition that can be called by add a reference variable.

def addition(a=10,b=2):
    print(a/b)
addition()

add=addition   #here add is the reference variable which point to addition function
add(10,3)

In Python, We can also call from one function to another.

Suppose we are creating another function which contains the address of function as an argument.

def incr(x):
    return x+1

def cfun(func,x):   #it is contain address of function in first argument and parameter value in second argument
    result=func(x)
    return result
data=cfun(incr,20)

print(data)

We can also return data from one function to another function using the nested form.

def addmain():
 def add():
    
    print("hello")
 return add   
x = addmain()
x()

Another best example of a function where we pass the method as an argument and call method under the inner method in Python.

def fun_main(func):
    def inner():
        print("Inner")
        func()
    return inner
def scs():
    print("Outer")
s = fun_main(scs)
s()

Decorator example in Python:- 

def fun(func):  #default without return type
    def inner(msg):
        print(msg,"inner")
    return inner    
@fun
def fun2(msg):
    print(msg)
fun2("welcome")

.......................................................................................................................................................

here @fun is decorator
def fun(func):  #default without return type
    def inner(msg):
        print(msg,"inner")
    return inner    
@fun
def fun2(msg):
    print(msg)

fun2("welcome")