Python decorators!

Posts about decorators

decorators 1 (this one)
decorators 2 – arguments to decorator
decorator 3 – more complex decorator
decorator 4 – reduce to extend functionality with decorators

One useful things are decorators. At the beginning can be a little intimidating and can confuse you, but are very simple to use once you get them. I made the most simple script I could make for this tutorial (code on github repository python_cheatsheet/decorator.py).

What is a decorator?

It is a function/decorator that can be used more times by different functions using simply a @ and the function name before the function that want to use the decorator

The flow chart of the usage of decorator:

make a decorator function that gets another function as argument and that has an inner function that has the arguments of the other function
the decorator function returns the innerfunction
the other functions have the @ followed by the name of the decorator funcion before the def statement
when you call the other functions, they will be passed to the decorator and the arguments will be passed to the inner function of the decorator
the code in the other functions is executed
the code in the inner function of the decorator is excuted

This way all the other functions will use the same code in the decorator in common, saving code and organizing code better. The code is also more mantainable.

The example

# decorators

def print_it(fn):
    def show_result(a, b):
        print(f"{fn.__name__}({a},{b}) is = to {fn(a, b)}")
    return show_result


@print_it
def add(a, b):
    return a +  b


@print_it
def subt(a, b):
    print("This is subt")
    return a - b


@print_it
def mult(a, b):
    print("This is mult")
    return a * b


@print_it
def div(a, b):
    print("This is div")
    return a // b

# add(5, 4) # 9
# print("Let's go to the other one")
# subt(2, 3) # -1
div(10, 5)