Python Decorator

🐍 When you need to use a function and add more code to it while retaining original function, you can use decorator.
A decorator is nothing but a function to which another function is passed, and both are run.
First we will look at Closure in Python. It is calling of a function inside another function from outside. Example of a Closure:

def one(func):

  def two(*args):

    print(f"You are running function {two.__name__} and have passed arguments as follows: {args}")

    print(f"Result of the two numbers {args[0]} and {args[1]} is {func(*args)}")

  return two

def addfunc(x,y):

  print("Addition")

  return x+y

def subfunc(x,y):

  print("Subtraction")

  return x-y




addouter = one(addfunc)

subouter = one(subfunc)

addouter(4,3)

subouter(4,3)

Output

You are running function two and have passed arguments as follows: (4, 3)

Addition

Result of the two numbers 4 and 3 is 7

You are running function two and have passed arguments as follows: (4, 3)

Subtraction

Result of the two numbers 4 and 3 is 1

1. Created function "one" with another function inside it named "two"
2. Function "one" returns function "two"
3. Function "two" calls the function passed to function "one"
4. We created two more functions named "addfunc" and "subfunc". These functions adds two numbers passed to it and subtracts two numbers passed to it respectively.
5. We passed these functions to function "one"

Now let's try the same thing using decorator

def one(func):

  def two(*args):

    print(f"You are running function {two.__name__} and have passed arguments as follows: {args}")

    print(f"Result of the two numbers {args[0]} and {args[1]} is {func(*args)}")

  return two

@one

def addfunc(x,y):

  print("Addition")

  return x+y



@one

def subfunc(x,y):

  print("Subtraction")

  return x-y



addfunc(4, 3)

subfunc(4, 3)

Output

You are running function two and have passed arguments as follows: (4, 3)

Addition

Result of the two numbers 4 and 3 is 7

You are running function two and have passed arguments as follows: (4, 3)

Subtraction

Result of the two numbers 4 and 3 is 1

Now we need not save returned function to call them. It can will be directly called and functions addfunc and subfunc will be passed as we used decorator