@

• @

def decorator(func):
    return func

@decorator
def some_func():
    pass

Is equivalent to this code :

def decorator(func):
    return func 
def some_func():
    return pass
some_func=decorator(some_func)

Example :

class Pizza(object):
    def __init__(self):
        self.toppings=[]
    def __call__(self, topping):
        self.toppings.append(topping())
    def __repr__(self):
        return str(self.toppings)

pizza=Pizza()

@pizza 
def cheese():
    return 'cheese'

@pizza
def sauce():
    return 'sauce'

print(pizza)

>>>
['cheese', 'sauce']

class DatetimeDecorator:
    def __init__(self, f):
        self.func=f

    def __call__(self, *args, **kwargs):
        print(datetime.datetime.now())
        self.func(*args, **kwargs)
        print(datetime.datetime.now())

class MainClass:
    @DatetimeDecorator
    def main_function_1():
        print('main function 1 starts')

    @DatetimeDecorator
    def main_function_2():
        print('main function 2 starts')

my=MainClass()
my.main_function_1()
my.main_function_2()

>>>

2021-12-21 06:17:35.554216
main function 1 starts
2021-12-21 06:17:35.555863
2021-12-21 06:17:35.556337
main function 2 starts
2021-12-21 06:17:35.556954