Decorator Beginner __name__ is causing Type error

Question

I have tried a few things to see if it had to do with when the functions were defined but to no avail I could not solve this. I am 90% sure the " name " method is causing the issue. But to me, this seems like it would be a good way to use a wrapper? Trying to explore wrapper because I am currently learning flask and they use wrappers off the get go with subdirectories. Thank you in advanced.

def smartCalc(func):
    def inner(a, b):
        if func.__name__ == "divide":
            print("I am going to divide" + str(a) + "and" + str(b))
            if b == 0:
                print("whoops! cannot divide")
                return
            return func(a, b)
        
        if func.__name__ == "Add":
            print("I am going to add", a, "and", b)
            return func(a, b)
        return inner



@smartCalc
def divide(a, b):
    print(a/b)

@smartCalc
def Add(a, b):
    print(a+b)



Add(3,1)

TypeError: 'NoneType' object is not callable I was somewhat following this when I wanted to try something.

Answer 1

You need to unindent the return inner , and execute func in all cases finally

def smartCalc(func):
    def inner(a, b):
        if func.__name__ == "divide":
            print("I am going to divide", a, "and", b)
            if b == 0:
                print("whoops! cannot divide")
                return
        if func.__name__ == "Add":
            print("I am going to add", a, "and", b)

        return func(a, b)

    return inner

Answer 2

Your smartCalc defines an inner function, and then doesn't do anything else. It doesn't call the inner function, nor does it return something. So it always returns None.

Remember how

@smartCalc
def Add(a, b):
    print(a+b)

is just a fancy way of writing

def Add(a, b):
    print(a+b)
Add = smartCalc(Add)

? Well, now Add is None , so you can't call it anymore.