Decorators

• takes A function that takes 1 function as input and returns another function
• my_decorator is a function that takes another function func as its parameter.

def my_decorator(func):
    def wrapper():
        print("Something is happening before the function is called: Inside my_decorator, a new function wrapper is defined.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

# Calling the decorated function
say_hello()

def document_it(func):
    def new_function(*args, **kwargs):
        print('Running function: ', func___name__)
        print('Positional arguments: ', args)
        print('Keyword arguments: ', kargs)
        result = func(*args, *kargs)
        print('Result: ', result)
        return result
    return new_function

• whatever func you pass to document_it(), you get a new function that includes the xtra statements that document_it() adds.

def add_ints(a,b):
    return a+b

add_ints(3,5)
# Output
8

cooler_add_ints = document_it(add_ints) # manual decorator assignment
cooler_add_ints(3,5)
# Output
Running function: add_ints
Positional arguments: (3,5)
Keyword arguments: {}
Result: 8
8

• as an alternative to the manual decorator assignment, you can add @decorator_name before the function

@document_it
def add_ints(a,b):
    return a+b
add_ints(3,5)
# Output
Start Function add_ints
Positional arguments: (3,5)
Keyword arguments: {}
Result: 8
8

• you can have more than one decorator for a function page160