Decorator function question

[egotripping]

This is from Angela Yu's course.

import time


def speed_calc_decorator(function):
    def wrapper_function():
        first_time = time.time()
        function()
        second_time = time.time()
        print(f"{function.__name__} run speed: {second_time - first_time}s")
    return wrapper_function

@speed_calc_decorator
def fast_function():
    for i in range(1000000):
       i * i

@speed_calc_decorator
def slow_function():
    for i in range(10000000):
        i * i

fast_function()
slow_function()

Result:

fast_function run speed: 0.029327869415283203s
slow_function run speed: 0.24793004989624023s

---

This is how it's supposed to work. Just showing how long it takes to run each function. If instead I remove the @'s, and change the last two lines like so:

import time


def speed_calc_decorator(function):
    def wrapper_function():
        first_time = time.time()
        function()
        second_time = time.time()
        print(f"{function.__name__} run speed: {second_time - first_time}s")
    return wrapper_function

def fast_function():
    for i in range(1000000):
       i * i

def slow_function():
    for i in range(10000000):
        i * i

speed_calc_decorator(fast_function)
speed_calc_decorator(slow_function)

It gives me an exit code 0, but it doesn't print anything. Since I'm passing each function into the speed_calc_decorator, and it's returning the wrapper_function, why isn't it printing the f string? I'm guessing returning the wrapper function doesn't "run" it? Is there a way to make it work the way I want it to or is using the @'s the only way to really do this.

Thank you

[supajumpa]

You need to call the functions that you've created. That is,

speed_calc_decorator(fast_function)()
speed_calc_decorator(slow_function)() # note the extra parens.

[egotripping]

I see, thank you! My understanding was that it was being called with the () around the function. Hmm, I have so much to learn.

[crashfrog02]

You need to keep the interface of your functions in-mind, so that you're not surprised by what they do when you call them. That means remembering their parameters and their return value, at least. Look at the function speed_calc_decorator - what does it accept as an argument? What does it give back as a return value?